Unveiling the potential of covalent organic frameworks for energy storage: Developments, challenges, and future prospects

REVIEW www.advenergymat.de Unveiling the Potential of Covalent Organic Frameworks for Energy Storage: Developments, Challenges, and Future Prospects Prashant Dubey, Vishal Shrivastav, Tribani Boruah, Giorgio Zoppellaro, Radek Zboˇ ril, Aristides Bakandritsos,* and Shashank Sundriyal* Covalent organic frameworks (COFs) are porous structures emerging as promising electrode materials due to their high structural diversity, controlled and wide pore network, and amenability to chemical modifications. COFs are solely composed of periodically arranged organic molecules, resulting in lightweight materials. Their inherent properties, such as extended surface area and diverse framework topologies, along with their high proclivity to chemical modification, have positioned COFs as sophisticated materials in the realm of electrochemical energy storage (EES). The modular structure of COFs facilitates the integration of key functions such as redox-active moieties, fast charge diffusion channels, composite formation with conductive counterparts, and highly porous network for accommodating charged energy carriers, which can significantly enhance their electrochemical performance. However, ascribing intricate porosity and redox-active functionalities to a single COF structure, while maintaining long-term electrochemical stability, is challenging. Efforts to overcome these hurdles embrace strategies such as the implementation of reversible linkages for structural flexibility, stimuli-responsive functionalities, and incorporating chemical groups to promote the formation of COF heterostructures. This review focuses on the recent progress of COFs in EES devices, such as batteries and supercapacitors, through a meticulous exploration of the latest strategies aimed at optimizing COFs as advanced electrodes in future EES technologies. P. Dubey Advanced Carbon Products and Metrology Department CSIR-National Physical Laboratory (CSIR-NPL) New Delhi 110012, India V. Shrivastav Institute of Physical Chemistry Polish Academy of Sciences Kasprzaka 44/52, Warsaw 01–224, Poland The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/aenm.202400521 © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. DOI: 10.1002/aenm.202400521 1. Introduction In recent years, highly porous organic polymers like hypercross-linked polymers (HCPs), porous aromatic frameworks (PAF), and conjugated microporous polymers (CMPs) have garnered profound attention as candidates in miscellaneous applications due to their unique features, such as tailored architecture, low density, and periodic porous network. Covalent organic frameworks (COFs) are such an emerging class of porous organic materials offering a wealth of benefits and have attracted substantial attention. COFs exhibit extended 𝜋-conjugated regions that are either stacked in-plane or perpendicularly, a large number of accessible sites for catalysis, sensing or electrochemical energy storage (EES), high structural diversity, intermolecular interactions, chemical functionalities within size-tailored cavities, and, importantly, a lightweight nature due to their low density.[1–5]Unlike the traditional crystalline porous solids such as zeolites T. Boruah School of Chemistry Cardiff University Translational Research Hub, Maindy Road, Cathays, Cymru/Wales, Cardiff CF24 4HQ, UK G. Zoppellaro, R. Zboˇ ril, A. Bakandritsos, S. Sundriyal Regional Center of Advanced Technologies and Materials The Czech Advanced Technology and Research Institute (CATRIN) Palacký University Olomouc Šlechtitel˚ u 27, Olomouc 779 00, Czech Republic E-mail: [email protected];[email protected] G.Zoppellaro,R.Zboˇ ril,A.Bakandritsos CEET NanotechnologyCentre VŠB−TechnicalUniversityofOstrava 17.listopadu2172/15,Ostrava,Poruba70800,CzechRepublic Adv. Energy Mater. 2024,14, 2400521 2400521 (1 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH www.advancedsciencenews.com www.advenergymat.de and metal-organic frameworks (MOFs), COFs are purely organic structures, granting them several distinct advantages: 1) highly modular structure owing to the diverse organic chemistry, allowing for structure-property relationships tuning and thus higher efficiency in certain applications; 2) enhanced stability compared to MOF since the latter are often susceptible to degradation due to the labile coordination bonds, while COFs can be synthesized to remain stable under variable conditions and are typically more robust; 3) cost-effectiveness, owing to their straightforward synthesis and use of inexpensive precursors; 4) non-toxic and environment-friendly nature due to absence of metal ions.[6,7] The synthesis of COFs can be traced back to 2005 when Yaghi et al. developed new organic frameworks by covalently linking organic molecules to form 2D extended structures, termed as COF1andCOF-5. [4]These COFs were based on boronate ester linkages and provided a fundamentally new way of constructing ordered, crystalline, and porous organic materials from molecular building blocks using strong covalent bonds. The boronate ester linkages, used to construct the frameworks, are reversible under certain conditions, and thus were essential for facilitating errorcorrection mechanisms during the self-assembly process and achieving crystalline materials. The primary building elements of COFs are organic monomers composed of light atoms (C, H, O, N, Si, B). Commonly used organic reactive linkers include, apart from boronate esters are boronate anhydrides, hydrazines, imines, and nitriles, which react via cyclotrimerization.[8]The intriguing properties of COFs, including the high structural control, the micro and mesopores, the wide availability and variability of functional groups, and the possibility for tailored chemical modifications to tune spins, photoexcited energy carriers (excitons, polarons) have rendered them as highly attractive materials for numerous applications. The intricate and tunable structural and physicochemical suite of compelling properties of COFs underscore their potential across diverse applications in a broad spectrum of disciplines, spanning from sensing,[9,10] environmental remediation,[11,12]separation,[13]and EES[14–16]to advanced domains of photo-/electrocatalysis,[17]spintronics,[18] optoelectronics,[19]and biomedicine.[20] COFs are emerging promising candidates as active materials in EES owing to their unique features arising by their framework which is rich in ordered in-plane or stacked 𝜋-conjugated motifs, stabilized by the organic linkers.[21]The key features rendering COFs attractive systems in EES embrace: a) the inherent and uniform porous architecture with ordered alignment, which provides a large specific surface area (SSA) and facilitates rapid ion transport pathways; b) the abundance of charge storage sites, such as pores and redox moieties; c) the enhanced mobility of the charge carriers is particularly promoted by the aromatic conjugated network, and ionic sites residing in side-functionalities of the linkers. The rich chemistry of COFs allows for precise tuning at the molecular level, enabling selective incorporation of various functional groups to enhance electroactive sites and optimize the charge storage process;[22–25]d) The high strength of the covalent bonds within COFs contributes to superior structural integrity, enabling them to withstand volume changes and structural deformation brought on by ion intercalation/deintercalation during cycling process; e) COFs predominantly consist of lightweight elements like C, N, and O, which may offer higher gravimetric capacitance compared to electrode materials that contain metals. These structural and functional features are crucial parameters for tailoring the properties of COFs, including charge storage capacity, electrochemical stability, and rate capability.[26,27]Therefore, COFs have generated extensive attention within the EES domain. This review gives an insight on the latest advances in the growing domain of COF materials, the pivotal role of their architectural design, synthesis methods and the underlying physical and chemical properties. A notable aspect of this review lies in the exploration of the diverse structures exhibited by COFs, achieved through the utilization of distinct building blocks with varying symmetries, while also delving into the advantages and drawbacks associated with different synthesis approaches. Furthermore, this review sheds light on the recent progress of COFs in the EES landscape encompassing metal ion batteries, supercapacitors, and metal ion capacitors. Their role as hosts for postlithium chemistries, as redox-active electrodes, solid-state ion conductors, polysulfide shuttling inhibitors, and electrode separators is also highlighted. Ultimately, this work concludes by addressing the existing challenges and promising future research directions in this emerging field. Figure 1shows the structural properties of COFs that are directly associated with the electrochemical properties targeting the EES applications. 2. Timeline of Advancements in the Field of COFs During the 20th century, the remarkable improvements in our understanding of covalent bonding in organic molecules led to a shift from an empirical approach toward a more rational design of organic molecules. Thus, the synthesis of COF materials has evolved substantially during the past 20 years, with multiple noteworthy turning points (Figure 2).[28,29]With the successful synthesis of the first COF structure, known as COF-1, and the visionary work of Yaghi and his coworkers, a new era emerged.[4]Following this breakthrough, the research in this field witnessed the birth of an exciting family of previously unexplored materials with an extraordinary opportunity of structural diversity and modulation. The groundbreaking structure of COF-1, based on benzene rings connected by atoms of boron and oxygen, laid the groundwork for further developments. By 2007, scientists showcased a wide range of COF structures through the use of different organic building blocks, demonstrating the growth possibilities of the COF family.[30]The field evolved as a result of these advancements, unlocking a wide range of organic framework architectures. The synthesis of imine-linked COFs, such as COF-5, was accomplished in 2009 by Furukawa et al. These compounds demonstrated improved stability and promising properties for use in gas storage and separation.[31]In 2011, a milestone discovery signaled a change in the field of COFs related to the synthesis of covalent triazine frameworks (CTFs).[32] COFs based on CTFs captured the attention of scientists with their outstanding thermal stability and broad potential in fields like gas storage/capture, and catalysis.[33–36]The COF landscape evolved further by the synthesis of extended 𝜋-conjugated COFs in 2013 by Yaghi et al., which introduced interesting new applications in optoelectronics and sensing.[37]Novel device designs and sensing platforms were made possible by the remarkable electrical characteristics demonstrated by these COFs with extended 𝜋-conjugated areas. The effective synthesis of dynamic Adv. Energy Mater. 2024,14, 2400521 2400521 (2 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de Figure 1. The distinct properties of COFs associated with the corresponding structural and physical properties targeting the EES applications. COFs, which are capable of reversible structural alterations, was another achievement in 2016. By creating novel materials that respond to stimuli, these adaptive COFs enabled the creation of tunable frameworks.[38–40]Synthesizing COF single crystals and thin films with regulated and extended crystallinity and orientation in 2018 was another milestone.[41,42]Following a two-step process, nanoscale seeds of boronate ester-linked 2D COFs were grown into micrometer-scale single crystals by using a solvent that suppresses the nucleation of additional nanoparticles, which otherwise mainly lead to amorphous powders. The extended crystalline solids displayed superior charge transport compared with that observed in conventional powders. This discovery increased the potential applications of COFs across a range of industries by making it easier to incorporate them into electrical devices and Figure 2. a) Timeline of the advancements in the COFs field; b) Number of publications investigating research on COFs in the last 12 years, as of Feb 2024 (as per Web of Science). Adv. Energy Mater. 2024,14, 2400521 2400521 (3 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de membranes. In 2018, free aldehyde synthesis of COF has been reported to lead to the opening of sub-stoichiometric synthesis capable of yielding either free amine or free aldehyde groups in imine-linked COFs.[43]Coupled with opportunities for functionalization, such as post-synthetic modification of frustrated groups, this method has facilitated the utilization of these networks in water harvesting, gas adsorption, and separation, as well as in various applications of photocatalysis.[44]Furthermore, the sub-stoichiometric approach was another recent development in COFs chemistry which typically results in unconventional topologies with free and active functional groups within the pores of these materials that are not present in the case of COFs with fully linked network nodes.[45]The production of redox-active COFs in 2019 which have the ability to store and release charge introduced new prospects for electrochemical and energy storage uses. Their applicability in sustainable energy technologies has been successfully demonstrated by these redox-active COFs.[25,46–48]A significant advancement in COF synthesis was achieved in 2021 when high-valency COF structures were successfully synthesized with extended connectivity of the building units.[49]These structures, based on multivalent polycubane linkers expanded the possible topologies for COFs by surpassing the previous valency limits of 3 and 4, dictated by the reliance on the sp2and sp3hybridization of carbon chemistry. This created new possibilities for applications in fields including drug delivery, sensing, and catalysis by providing enormous surface areas and customizable architectures. 3. Engineering Aspects Governing the Design of COF-Driven Electrode Materials 3.1. Architectural Design Strategies Generally, the morphology, dimensions, and configuration play a critical role in determining the structure of COFs. Utilizing topological diagrams, one can effectively predict the growth mechanism of COFs.[8]The core growth of the COF is depicted in the topological schematic of Figure 3a, which indicates the sequential formation of covalent links within the propagating polymer chain. For the directional control of bond formation, the monomers—or foundational building blocks—are engineered with rigid backbones. These backbones include reactive functional units in a geometrically predefined arrangement, facilitating the precision construction of the COF architecture. The assembly of planar monomers culminates in a well-defined polymeric architecture, terminating at a specific juncture to yield 2D atomic layers, each exhibiting distinct topologies.[50–55]These 2D layered structures are marked by an alignment of 𝜋-conjugated blocks affixed onto the atomic planes, predominantly arising through 𝜋–𝜋stacking interactions.[7]In such an arrangement, interlayer non-covalent interactions promote structural stability, whereas the robust intra-layer covalent bonds secure the framework’s integrity. COFs exhibit significant advantages connected to their diverse skeleton designs and rich porous networks, which give rise to a great variety of COF architectural motifs, including, but not limited to, imine-linked COFs, hydrazone-linked COFs, and keto– enol-linked COFs.[56,57]Primarily, ordered 1D channels are created by the covalent assembly of 2D COFs, which are 2D polymers in the x and y directions that stretch and aggregate in the z-direction. The interlayer interactions in these 2D polymers eventually lead to the formation of a layered structure[51,58].The intrinsic growth mechanism of COFs facilitates their uniform propagation in a specified direction, contributing to the high crystallinity and lattice precision often observed in these materials. Due to the layered configuration, each monomeric unit is superimposed over two adjacent monomeric units, further promoting the overall stability and dictating the orientation of neighboring layers. Conversely, the construction of 3D COFs involves the multidirectional extension of the polymeric backbone, leveraging a synthesis strategy that combines chain folding with layeroverlapping methodologies. This expansion is not merely spatial but also functional, providing these materials with a dimensional versatility that enables their application in a broad field of technological frontiers. This functional adaptability confers upon these materials a dimensional versatility that is pivotal for their integration into a wide spectrum of technological applications, from gas storage and separation to catalysis, sensing, and drug delivery.[59–63] 3.2. Structural Diversification: Building Units The topology diagram serves as the blueprint for engineering intricate frameworks within 2D or 3D COFs. These frameworks consist of interconnected lattices formed by assembling building block units, resulting in periodically arranged knots and linkers. The strategic selection of aromatic monomers, known for their versatile geometries, allows for the topologically guided synthesis of COFs. In this context, it is crucial to identify the symmetry components, particularly the rotational symmetry associated with the relevant monomers. This can be achieved by determining the rotational axes of the monomers. Aromatic rings, recognized for their rigid structures, are favored as the fundamental units for supporting well-ordered growth pathways within both 2D and 3D architectures. To leverage the inherent order dictated by the topology and to maintain the planarity of extended COF structures, the integration of rigid building blocks is a common strategy in COF construction. Their rigidity is conducive to the formation of coordination bonds, guiding the linear and planar extension of the COF backbone in a spatially organized manner. Various building blocks, including but not limited to extended 𝜋-conjugated systems, macrocyclic structures, and nitrogen or sulfur-rich components, have been synthesized enriching the toolkit for structural and functional control. According to the topological map, these COFs exhibit an extensive array of skeletal topologies and pore configurations. The diversity of 3D COFs heavily relies on the choice of monomeric units, which not only dictates the framework’s topology but also its functionality. Despite the constraints imposed by the pursuit of Td-symmetry or orthogonal termini, these units offer a valuable pool for structural variation. The backbone of COFs can adopt an array of configurations, ranging from basic geometries from benzene and heterocyclic motifs to macrocycles like octahedra, as well as different configurations such as C2, C3, C4, and Td. Moreover, monomeric units extend beyond their role in shaping the COF structure; they also Adv. Energy Mater. 2024,14, 2400521 2400521 (4 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de Figure 3. a) Topology diagram of COFs with different structures and building blocks, b) redox-active groups used in COFs, and c) Different linkers and bond formation leading to COF synthesis. Reproduced with permission.[25]Copyright 2021, John Wiley & Sons. endow the framework with a plethora of additional features. These features encompass the provision of docking sites for guest molecules, the introduction of active sites for catalysis, the creation of chiral centers for enantioselective applications, and the integration of photosensitive elements for energy and sensing applications. 3.2.1. COFs in the 2D Architectural Domain The domain of 2D COFs is distinguished by a wide range of architectural configurations. These structures can be engineered to exhibit both isotropic and anisotropic polygonal skeletons, with each configuration dependent on a carefully chosen array of Adv. Energy Mater. 2024,14, 2400521 2400521 (5 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de linkers and building blocks. Typically, each design relies on a significant number of linkers and construction blocks. By employing diverse monomer geometries within the topological framework, various skeletal and pore configurations can be achieved, resulting in distinct 2D frameworks with diverse arrangements of pores and skeletons (Figure 3a,b).[24,50,52,64–66] For instance, COF engineering can involve the utilization of C2, C3, C4, and C6 symmetric linkers as the knots for fabricating 2D COFs with rhombic, trigonal, tetragonal, hexagonal, and kagome geometries. By linking C2-symmetric units to other C2 or C3-symmetric counterparts as knots, in combinations such as [C3 +C3], [C2 +C2 +C2], and [C3 +C2], hexagonal two-dimensional COFs with distinct pore size distributions, arrangements, and spacing between pores can be synthesized. Conversely, tetragonal COFs, characterized by four-sided geometries, can be synthesized using [C4 +C2] and [C4 +C4] linkages.[67–72]Additionally, the synthesis of triangular and rhombic crystal lattices, featuring dual pore networks and symmetric termini, is achievable.[73]In comparison to other C2-symmetric knots that form rhombic polygons, the use of C2-symmetrical knots with larger aromatic systems and the incorporation of C3symmetric macrocycles can facilitate strong interactions, often leading to the formation of kagome-type geometries. For example, the use of C3-symmetric macrocyclic can produce kagome COF with six triangular apertures on the periphery, and a dodecagonal aperture in the center (Figure 1a). However, the final morphology of a single COF crystal can be influenced by factors such as the dimensions and strength of the inter-layer interfaces, as well as the overall bulkiness and steric effects of the knot unit.[74,75] 3.2.2. COFs in the 3D Architectural Domain The design of 3D COFs requires at least one building unit with tetrahedral or orthogonal geometry. These fundamental geometries are pivotal as they enable the polymer chains to propagate into an extensive covalently bonded 3D network (Figure 3b). Furthermore, by integrating tetrahedral or orthogonal nodes, 3D COFs can be architecture to allow the twisting and interlacing of polymer chains in multiple dimensions, culminating in the formation of intricate 3D skeletal structures and porosity (Figure 3b).[51,66,76–78]For example, the combination of Td + C3 symmetries can produce skeletal networks with dramatically improved surface areas.[79–81]Conversely, the interplay between Td and C2 symmetries can yield [Td +C2] and [Td +Td] layouts, which offer a diverse range of 3D COF structures due to the inclusion of linker units possessing C2 symmetry.[82–84]In these cases, tailored configurations of polymer backbones and the strategic interlacing of polymer chains are harnessed to engineer one-dimensional channels. These channels typically exhibit pore diameters ranging from 0.7 to 1.5 nm, classifying them within the microporous regime. The [Td +C2] and [Td +C4] layouts are employed to construct appropriate network nodes resulting in two-fold interpenetrated 3D COFs (using two C2or C4symmetric units with four reactive sites).[77,85,86]For example, 3D COF-505 illustrates a helical structure that integrates an orthogonal Cu(II) complex with phenanthroline moieties acting as the knot, interconnected by C2-symmetrical linkers.[76] Despite the advancements in 3D COF design, the current topological models cannot precisely predict the fold multiplicity or control the folding patterns within a given COF, rendering predesigned and synthetically programmable 3D COFs a rarity. Consequently, regulating the ultimate properties of COFs by anticipating the degree of interpenetration and folding patterns remains a formidable challenge. Nevertheless, these complexities present a fertile ground for innovation, particularly at the nexus of computational design and artificial intelligence. 3.3. Diversification of Linkage In the realm of COFs, the diversification of linkage groups plays a pivotal role in dictating their structural and functional attributes. Predominantly accessible linkage groups include boroxine, boronate-ester, borosilicate, imine, hydrazone, borazine, squaraine, azine, phenazine, and imide, with C═C, azine, hydrazone, boronate-ester, imine, and boroxine (Figure 3c) being the most frequently employed.[87,88]These linkages are central to the synthesis of COFs, often leveraging reversible covalent bonds to impart distinct properties, such as high crystallinity via dynamic covalent chemistry.[89]For example, pre-organizing monomers using a reversible and removable covalent linkage. This method produced highly crystalline imine COFs with increased porosity, ascribing to the obtained COF superior charge carrier transport, and photocatalytic hydrogen evolution. The synthesis of COFs substantially relies on the solvent medium, typically a combination of polar and nonpolar solvents. Strategic choice of solvents and combinations facilitates the manipulation of solubility parameters, crucial for enabling optimal conditions for bond formation. Moreover, the thermodynamics of the synthesis is influenced by several key factors: the nature of solvent interactions, the presence and type of catalysts, solvent effects on catalytic organic bond formation, the reaction temperature, and the duration of the synthesis. Each of these elements plays a vital role in steering the reaction towards the desired product. Furthermore, the ability to fine-tune the synthesis conditions allows control over additional aspects, since by adjusting the combination and ratios of the linkages, COFs’ crystallinity, porosity, and overall composition can be tailored. This versatility in synthesis underscores the potential of COFs as modular materials with attractive functionalities and applications in diverse scientific fields. 4. Synthesis Methods for COFs A multitude of synthesis methods have been developed for the creation of COFs, including solvothermal, microwave, mechanochemical, and room temperature approaches, among others[90](Figure 4). It is crucial to understand the influence of the synthesis method on the physical and chemical properties of COFs, as this knowledge is essential for tailoring the qualities of COFs for specific applications. For example, the synthesis of COFs relies on the dynamic covalent chemistry (DCC) approach, because it is well known to produce extremely crystalline and thermally stable structures.[8]The porous nature of COFs arises from their organic chemical constituents, enabling the precise integration of organic building components, enables the precise Adv. Energy Mater. 2024,14, 2400521 2400521 (6 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de Figure 4. Different approaches for the synthesis of COFs (solvothermal and microwave, reproduced with permission,[115]Copyright, 2015, Royal Society of Chemistry; room temperature, and interfacial synthesis, reproduced with permission,[116]Copyright 2015, Springer Nature; surface mediated, reproduced with permission,[117]Copyright 2017, Royal Society of Chemistry; and flow synthesis, reproduced with permission,[118]Copyright 2015, John Wiley & Sons). integration of organic building components, which is essential for optimizing their performance in energy storage devices. In 2005, Yaghi and his team successfully synthesized the first COF by molecular dehydration of 1,4-benzene diboronic acid.[4]Since then, extensive research has been conducted to explore novel methods of COF synthesis. COFs of diverse morphologies, including sheet, fibrous, petal, and spherical COFs, as well as intricate topologies, such as rhombic and hexagonal, quadrangular, and trihexagonal COFs, can be produced using a wide range of organic monomers and functional groups.[91,92]Various synthesis techniques can be employed to combine such 2D and 3D topological COFs, often modified with side functional groups.[93] In addition, the well-organized or crystalline structure of COFs can be pre-designed by adjusting the proportions of constituent molecules and linkages, altering reaction conditions, or selecting alternative monomers as organic building blocks. The architecture, size, and porosity of COFs can be further adjusted by modifying the molecular geometry and concentration of the building blocks. Different synthesis methods offer unique opportunities to control the morphology, structure, and properties of COFs to meet the material requirements for energy storage applications. In terms of material requirements for energy storage applications, synthesized COFs should possess specific characteristics such as i) high surface area to provide ample active sites for charge storage, ii) porosity and crystallinity for efficient electrolyte penetration and ion diffusion, iii) stability to withstand the electrochemical stresses encountered during chargedischarge cycles, iv) conductivity to facilitate electron transport within the material, and v) tunable morphology and structure to optimize performance for different types of energy storage devices (e.g., capacitors, batteries). For instance, the solvothermal method allows for the precise control of reaction conditions, resulting in highly crystalline COFs with well-defined structures. These COFs typically possess high surface areas and tailored pore structures, making them suitable for applications requiring efficient electrolyte penetration and ion.[30,94,95]On the other hand, microwave-assisted synthesis offers advantages in terms of efficiency and speed, which can be beneficial for scaling up the production of COF materials for energy storage devices. However, keeping high crystallinity is one of the major concerns in the microwave synthesis method which is critical for the effective exploitation of the porous network to attain the fast insertion/de-insertion of ions. Regarding this, Cooper et al. discovered that adding a catalyst during microwave synthesis could improve the crystallinity of the product.[96]In the general microwave synthesis of covalent triazine frameworks (CTF), CF3SO3H was used as a catalyst which drastically improved the crystallinity. The efficiency and speed of microwave synthesis can be advantageous for scaling up the production of COF materials for commercial applications. The mechanochemical synthesis approach allows for the synthesis of COFs under ambient conditions, offering simplicity, scalability, and environmental friendliness by omitting harmful organic solvents.[97]The mechanism underlying mechanochemical organic synthesis is still not fully understood, although it is hypothesized that the formation of low-melting eutectic intermediate phases may facilitate covalent bond formation during the process.[98]The main downside of the mechanochemical synthesis is the very low SSA and crystallinity of the COF than that of other methods (70-100 m2g−1).[99,100]However it has been reported that mechanochemical synthesis could exfoliate the COF layers down to 10–30 layers, improving the ionic conductivity.[101]Moreover, mechanochemical synthesis methods conducted at room temperature provide mild conditions for COF formation, potentially leading to the production of COFs with enhanced stability. The ionothermal synthesis can produce highly crystalline COFs, but this method is mainly suitable for someCTFs.[102]Bytailoringthesynthesismethodandconditions, Adv. Energy Mater. 2024,14, 2400521 2400521 (7 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de research endeavors aim to control the properties of COFs to meet the requirements in terms of structural features and physicochemical properties which are appropriate for enhancing their performance in energy storage applications. Additionally, ongoing research into novel synthesis techniques and functionalization strategies are anticipated to further expand the range of COF materials available for energy storage technologies. 4.1. Solvothermal Synthesis The synthesis of COFs has predominantly relied on the solvothermal synthesis method,[103]a technique that involves hightemperature and high-pressure reactions between the monomers dissolved in a solvent (typically non-aqueous), in a sealed environment.[104,105]This method, pivotal in COF production, is instrumental in determining the resultant COF’s structural, physical, and chemical attributes. Typically, the monomer dissolved in a solvent is contained in a pyrex tube for a specific amount of time at a specific temperature to produce the COF product as a precipitate.[106]Key parameters such as reaction temperature, duration, pressure, and solvent choice significantly influence the structure, and thus the physical and chemical properties of the resulting COFs. Most COFs can be synthesized within a temperature range of 85–120 °C, depending on the reactivity of the organic monomers.[107]However, certain COFs, utilizing Schiff-base chemistry, require higher temperatures and longer reaction times, spanning from two to nine days.[3]Generally, in most synthesis methods for COFs, a minimum of three days is required for the completion of reactions and obtaining the product with a high yield.[95,108,109]For the production of thin films, the general experimental procedure involves immersing the appropriate substrate in the solvothermal reaction mixture. Han et al. used solvothermal processes to synthesize novel imine-linked chiral COFs, and used them for the separation of racemic alcohols.[110]However, the presence of a catalyst (acetic acid) led to the formation of amorphous polyimine sediments, thereby impeding the growth and nucleation of COFs. To bypass this, recently, Zhao et al. proposed a modified synthetic method for producing imine-linked COFs, utilizing the tert-butyloxycarbonyl (Boc) as a protective agent for the amine group to prevent the formation of amorphous polyimine.[111] Similarly in another report, Wang et al. reported the synthesis of COF-LZU1 using a solvothermal method by submerging a substrate into a reaction mixture containing an amine-protecting compound, 4-(tert-butoxy-carbonyl amino)-aniline (NBDPA).[112] The resulting thin films exhibited aligned structure and consistent thickness, composed of highly homogeneous protonated COF crystals interconnected by imine groups. Characterization of the produced COF thin films with the highly aligned structure showed a consistent thickness of 190 nm, which could be tailored by varying the monomers concentrations in the reaction mixture, the solvents, and the immersion duration. These studies demonstrated that this technique is quite effective for growing COFs with high crystallinity and orientation. Additionally, solvothermal methods were employed to synthesize a highly porous COF (TpPa-1) and its application as hydrophilic material for N-linked glycopeptides enrichment.[113]Additionally, COF-5 was produced by polymerizing 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) and 1,4-phenylenebis (boronic acid) (PBBA) in a pyrex capillary tube using dioxane and mesitylene as a solvent.[114]The reaction mixture was heated for 72 h at 100 °C to produce the COF as a powder. Recent studies have demonstrated the significant influence on the development of COFs of suitable growth substrates with good adhesive properties. One promising candidate for facilitating COF growth is single-layered graphene (SLG), known for its intriguing photoelectric properties. SLG can serve as an effective interface between COF and other substrates, improving the growth quality. Notably, Colson et al. achieved highly oriented COF growth over SLG and observed further enhancement of the orientation when using substrates such as Cu, SiC, and SiO2.[119,120]Specifically, the solvothermal condensation of 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) and phenylene bis(boronic acid) (PBBA) at 90 °C in a solution of mesitylene and dioxane over SLG/Cu substrate was used to grow COF-5. The produced COF-5 film exhibited hexagonal lattice grains parallel to the SLG. When SLG was used as a thin coating for other substrates, such as transparent fused SiO2, the substrate still significantly impacts the quality of thin films, affecting parameters such as thickness and uniformity. Thicker films were produced on the SLG/Cu substrate compared to the SLG/SiO2substrate, although the growth reaction was performed for the same time. Using the SLG/Cu substrate, thin films ranging from 30–37 nm of HHTPDPB COF and a series of Zn phthalocyanine (ZnPc) COFs were successfully grown. In an interesting report, Medina et al. demonstrated that 𝜋–𝜋interactions within the COF material are not necessary for the formation of oriented COF thin films over substrates.[121]A thiophene-based BDT-COF was successfully produced over an indium-doped tin oxide (ITO) and NiO/ITO coated glass substrates, with a thickness of 150 nm, and a highly crystalline nature, as demonstrated from the high-intensity diffraction peaks in XRD. Analysis of the diffractogram verified that the obtained COF thin film structure corresponded to a hexagonal unit cell with a lattice constant of a =b=36.9Å. This study confirmed that COF thin films can be produced on polycrystalline inorganic substrates (such as glass covered with NiO/ITO) without compromising the film quality. Ding et al. validated this finding by producing a TTF-COF over a Si/SiO2substrate and ITO-coated glass employing the solvothermal synthesis method.[122] In addition to the other factors, the chemical stability of COFs, especially in water and acidic environments, remains a critical consideration, particularly for energy storage applications. Previous studies have demonstrated that COFs linked by bketoenamine bonds exhibit high stability in aqueous and acidic environments.[123]By leveraging these findings, DeBlase et al. disclosed a modified solvothermal synthesis for the production of a COF based on ketoenamine-linked anthraquinones (DAAQ– TFP COF).[124]Instead of immersing the substrate in the reaction mixture, they achieved the formation of a disordered thin film with a thickness of 300–400 nm by adding triformylphloroglucinol (TFP) to a solution of 2,6-diaminoanthraquinone (DAAQ), which was prior deposited on an Au substrate. The starting concentration of the reaction monomers was varied to achieve control over the film’s thickness. The b-ketoenamine COF (DAB-TFP COF) thin films were also successfully produced using various substrates (indium tin oxide, fluorine-doped tin oxide, silicon, Adv. Energy Mater. 2024,14, 2400521 2400521 (8 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de and platinum). This COF, synthesized through the condensation of p-phenylenediamine (DAB) with 1,3,5-triformylphlorogluciol (TFP), was grown solvothermally and formed oriented thin films.[125]Two strategies were developed to fabricate well-defined metal/COF multi-layered structures and to pattern the obtained COF thin films. The first strategy involved alternating physical deposition of metal and chemical deposition of COF, while the second strategy utilized photolithography and reactive ion etching techniques. 4.2. Microwave Synthesis Typically, microwave synthesis refers to the application of microwave irradiation during the reactions performed for COF synthesis. Microwaves promote the reaction rate and lead to the reaction products in shorter times.[126,127]Microwave irradiation during synthesis can be also applied in synergy with solvothermal techniques, considerably decreasing the time and enhancing the yield. To exploit the microwave irradiation, the reaction mixture must contain a polar solvent. Cooper and his group pioneered on the microwave synthesis of boronate ester-linked COFs (COF-5 and COF-102).[109,128]These COFs were produced about 200 times faster than they would have by conventional solvothermal synthesis. It was discovered that the COF-5 produced using the microwave method had a significantly larger SSA than the COF-5 produced using the traditional solvothermal process. Similarly, Wei et al. produced a 2D enamine-linked COF-TpPa using a microwave synthesizer.[129]The microwaveassisted solvothermal method resulted in a COF with a highly ordered crystalline structure, while synthesized rapidly. This was combined with superior stability, maintaining its structural integrity under nine different solvents and enhancing its practical applications. COF-TpPa displayed as well an SSA of 724 m2g−1, and a high CO2capacity combined with adsorption selectivity for CO2over N2. In this regard, the utilization of the microwave-assisted solvothermal method in COF synthesis emerges as a highly advantageous approach offering notable structural benefits, combined with rapidity, affordability, and simplicity. Consequently, it holds significant promise for facilitating the large-scale manufacturing of COFs at a reduced cost. It is worth noting that the microwave synthesis method has not yet been widely employed for synthesizing a diverse range of COF structures. It should be noted, however, that precise calibration of reaction parameters is of utmost importance when aiming to achieve controlled synthesis of COFs. This necessitates conducting elaborate and multiple experiments to fine-tune the conditions. 4.3. Room-Temperature Synthesis Despite the excellent thermal and acid-base stability exhibited by room-temperature synthesized COFs, their applications remain limited, and only a few reports have been published to date.[130]The formation of COFs generally involves the reaction of organic building blocks that must undergo specific bondforming reactions, such as condensation or nucleophilic substitution, to create the covalent bonds that hold the framework stable. Usually, these reactions require an activation energy, which is typically provided by heating. Therefore, achieving controlled and efficient assembly of COF structures under room temperature conditions has been challenging. In 2005, Yang et al. proposed a straightforward solution-phase synthesis approach for the room-temperature formation of COF(TpBD).[131]Following straightforward synthesis steps, the produced COF exhibited improved thermal stability, but the yield and crystallinity were low. In another report, Lin et al. reported the synthesis of COFs at ambient temperature for the extraction of proteins from biological samples.[132]The COFs were obtained via the reaction between 1,3,5-tris(4-aminophenyl) benzene and terephthaldicarboxaldehyde, and were stable in water, organic solvents like methanol and THF, 10 mm HCl, and 1 mm NaOH at room temperature overnight, demonstrating the good chemical stability due to the strong C═N covalent bond formed, resulting to a polyimine-linkage skeleton. The same group also demonstrated the room-temperature synthesis of COFs by using 1,3,5triformylbenzene (Tb) and benzidine (BD) as ligands.[133]It is interesting to note that these COFs were synthesized on the surface iron oxide magnetic nanoparticles, which facilitated the magnetic separation of the COFs after the biological separation processes. Nevertheless, the metal centers on the surface of the magnetic nanoparticles could possibly play a crucial role in catalytic bond formation of the COF linkages at room temperature. Medina et al. established a modified method for the preparation of COFs at room temperature involving the conversion of the reaction mixture via a vapor-assisted approach.[121] This method allowed the control of various physical aspects of the COF. Changing the linker composition facilitated the control of periodicity/crystallinity, while droplet volume and solution concentration affected the thickness, porosity, and grain boundaries. To demonstrate this, BDT-COF and COF-5 based on benzodithiophene were prepared. The benzodithiophene diboronic acid (BDTBA), HHTP, dry acetone, and pure EtOH were all subjected to ultrasonication before being passed through a syringe filter in a concentration ratio of 0.025 mmol: 0.017 mmol. The 150 μL of BDTBA/HHTP filtered mixture was then applied to a glass substrate using the drop-casting technique, followed by exposure of the glass substrate to mesitylene and dioxane vapors in a vacuum desiccator. After 72 h, this resulted in the growth of a 7.5 μm thick dark green organic thin film. By reducing the droplet volume and solution concentration, the thickness of the resulting film could be adjusted. For example, using the same concentration but with a reduced droplet volume of 60 μL, a 2 μm thick film could be produced, while using 60 μL of a droplet with one-third of initial concentration, a thin film of 300 nm was produced. This highly effective technique can also be used to synthesize other COFs. While room temperature synthesis methods offer unique advantages such as simplicity and environmental friendliness, they are limited by the solubility of building monomers and the inability to synthesize a wide range of COF linkages and structures. Temperature plays a crucial role in the synthesis of COFs, allowing the introduction of new monomers and facilitating the combination of COFs with other materials. Despite the limitations, these reports highlight the promising potential of roomtemperature synthesis methods in various research areas, paving the way for future investigations of room-temperature-derived COFs. Adv. Energy Mater. 2024,14, 2400521 2400521 (9 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de Figure 6. a) Synthesis of different fluorinated COF structures, b,c) rate performance of different fluorinated COF and chlorinated COF. Reproduced with permission.[205]Copyright 2020, American Chemical Society. and cations during charge/discharge processes. Due to these exceptional qualities, the cathode material outperformed many organic cathode materials, as well as chlorinated COFs in terms of capacity (250 mAh g−1at 0.1 A g−1), swift kinetics (105 mAh g−1 at 5.0 A g−1), and remarkable cycle stability (95.8% capacity retention over 2000 cycles and 99.95% of coulombic efficiency). Composites@COFs as Cathodes: Covalent triazine frameworks, a form of COF, have been explored with great interested due to the n, p doping mechanism that they offer and which endows such materials with substantial lithium ion storage properties.[58,206–208]Their particularly small micropores and low conductivity, however, prevent counter-ion transfer, allowing Adv. Energy Mater. 2024,14, 2400521 2400521 (16 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de for capacities bellow the theoretical predictions. Growing CTFs with variable dimensionalities on carbon-based conductive materials or other conducting scaffolds, like MXenes, have been thus considered as promising routes to address this matter. Furthermore, the development of hierarchical pore architectures may further enhance electron conduction and ion transport routes. In this regard, 2D rGO & CTF have been studied for such synergistic integration, demonstrating features such as superior structural functionality and potent planar intermolecular conjugation. Zhang et al. integrated rGO with CTF using an in-situ polymerization process.[209]The composite exhibited considerable surface area of 1357 m2g−1, a high capacity (235 mAh g−1after 80 cycles at 0.1 A g−1), and remarkable stability (127 mAh g−1sustained after2500 cycles). Additionally, the extended and hierarchical pore architecture enhanced the Li+adsorption. During CTF’s operation as cathode persistent bipolar-redox reactions take place over a broad voltage range, enabled by the reversible n/p-doping mechanisms. The covalent triazine-based frameworks were reduced and regulated by Li+cations as a consequence of the ndoping technique, as illustrated in the equation: C3N3+xe−+xLi+=[C3N3−x(Li+)x](1) In another report, poly(imide-benzoquinone), a 2D microporous COF that was synthesized by in-situ crosslinking on graphene (PIBN-G), was tested as a cathode component for LIBs.[201]The integration of graphene with PIBN enhanced the charge transfer phenomena which further allowed the electrons and Li+to immediately access the redox-active carbonyls. Consequently, reversible specific capacities of 271.0 and 193.1 mAh g−1 were achieved at 0.1 and 10 C, respectively, while retention of more than 86% was achieved after 300 cycles. The process of discharging and charging involved the exchange of 8 Li+and 2 Li+ between the carbonyls of the imide and quinone units, respectively. Moreover, electroactive molecules can be grafted on conducting backbones,[210]converted into a salt,[211]or insoluble polymeric materials, which is crucial for preventing the dissolution of such small molecules in the electrolytes.[212]Polymeric materials are beneficial backbones since their molecular building blocks can be chemically modified leading to diverse architecture selected to enhance performance.[213]Polymerization also helps to reduce active material breakdown during cycling. Such polymeric electrodes retain their capacity better than monomers containing conjugated carbonyl groups.[214]For instance, a microporous poly-arylimide COF and CNT composite was developed using an in-situ polymerization process, which demonstrated an impressive 99.5% capacity retention over 8000 cycles.[168]Gao et al. presented additional results where rGO was used to create PIXCOF (where PI is polyamide and X is the concentration of rGO) composite materials through in-situ polycondensation method, and were evaluated as redox-active cathode electrode materials for LIBs.[215]Through this synthetic strategy, the PI-COF displayed small particle size, and thus increased exposed electroactive surface area. This facilitated swift transfer of electrons and Li+ion migration to the redox-active sites consisting of carbonyl groups. The composites, consequently, showed enhanced specific capacities, with PI50 having the highest, of 172 mAh g−1 at 500 mA g−1. The involvement of C═O double bonds in the redox process was demonstrated by FT-IR spectroscopy, which revealed their participation in the redox reactions. Similarly, in another report, the conjugated porous framework (CPFs), IEP11 was reported comprising different conductive constituents, including MWCNTs, SWCNTs, and rGO. This COF structure exhibited redox-active anthraquinone building blocks, while the addition of nanocarbon (rGO and SWCNTs/MWCNTs) during the polymerization step led to the production of thick bucky-paper electrode having high mass loading (60 mg cm−2)andactivematerial content (80 wt%) (Figure 7a–d).[216]The development of self-supported, binderand metal current collector-free, as well as high-mass-loading electrodes was possible by the incorporation of SWCNTs, which provided interconnected channels and mechanical stability. The high-mass-loading electrode demonstrated an unparalleled areal capacity of 6.3 mAh cm−2at 0.03C and a gravimetric capacity of 83.7 mAh g−1.Inanotherexample,anew redox-active conjugated microporous polymer (RCMP) was introduced based on anthraquinone moieties (IEP-11), synthesized through a novel two-step pathway combining miniemulsion and solvothermal techniques with solvothermal treatment through Sonogashira cross-coupling reaction. This method resulted in polymer nanostructures that were easier to disperse in solvents and fabricate electrodes. EP-11 exhibited a dual porosity, combining micro and mesopores, with a specific surface area as high as 2200 m2g−1, one of the highest values reported for RCMPs. When tested as a cathode in Li-ion batteries, the electrode delivered gravimetric capacities around 100 mAh g−1and extraordinary rate capability, retaining 76% of discharge capacity when charged and discharged in just 12 minutes (5C). Additionally, the insoluble and robust conjugated porous structure of IEP-11 provides unprecedented cycling stability, retaining ≈90% and 60% of its initial capacity after 5000 and 80 000 cycles, respectively.[217] When RCMP was treated for a longer time under hydrothermal conditions, the electrodes could be effectively compressed, leading to a density three-fold higher than the EP-11 electrode. Therefore, the compressible electrode displayed dramatically higher volumetric capacity. Moreover, the insoluble and robust conjugated porous structure imparted unprecedented stability, retaining 90% of the initial capacity after 5000 cycles at 2 C. In another report, a surface-controlled synthesis methodology was developed employing a pseudo-capacitive active anthraquinone-built COF (AQ-COF) composite with CNTs in a coaxial architecture.[218]AQ-COF was polymerized on the surface of CNTs to improve their dispersibility, processability, and electrochemical characteristics. The sample showed outstanding rate and cycle efficiency (100% capacity retention after 3000 charge/discharge cycles) attributed to the rapid surfacecontrolled redox processes, in conjunction with the conducting channels created by the presence of CNTs, favorable for the superior charge-transfer capabilities. COF structures have been also developed to harness the advantages of nickel-enriched layered metal oxides cathodes (e.g. NCM811) due to their exceptional capacity for lithium storage (200 mAh g−1),[219]which however, are limited by low structural stability and restricted life cycle, owing to the strong Li cation interaction and mismatch with the metal oxide crystals. To address this issue, a pyrazine-2D COF surface coating for the nickel-enriched layered metal oxides (NCM811) was designed.[220]The 2D planar structure and conjugated bond orientation of pyrazine not only shielded NCM811 against Adv. Energy Mater. 2024,14, 2400521 2400521 (17 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de Figure 7. a) Synthesis route for IEP-11 polymer and IEP-11-Xy hybrid materials, b) electrode preparation method for high and low mass loading, c) charging/discharging comparison of IEP-11-XY (where, X is MWCNTs(M), SWCNTs(S), RGO(R), and Y is wt% composition), and d) aerial capacity vs aerial current for different COF samples. Reproduced with permission.[216]Copyright 2020, American Chemical Society. Adv. Energy Mater. 2024,14, 2400521 2400521 (18 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de Figure 8. a) Diagrams illustrating the ion-conducting behavior and diffusion energy barrier in liquid, conventional solid, and COF conductors, respectively. b) Diagrams depicting the ion transport pathway in solid or liquid rechargeable batteries. Reproduced with permission.[102]Copyright 2022, John Wiley & Sons. transition metal diffusion, but also generated a metal cation blended layer that prevented irreversible intercalation of Li cations. The integration of COFs@composites with various materials, such as graphene, nanocarbon, and conjugated microporous polymers, has shown promising results in enhancing the performance of cathode materials for LIBs. The use of hierarchical pore architectures improves Li+adsorption and enables bipolarredox reactions over a wide voltage range whereas, incorporating graphene/CNTs like structure into COFs enhanced charge transfer, facilitates electron and Li+access to redox-active sites, leading to improved cycling stability. Comparatively, the incorporation of graphene and nanocarbon into COF structures shows promise in achieving enhanced conductivity and charge transfer, while surface-controlled synthesis methodologies offer opportunities to improve structural stability, making them attractive avenues for further research and development in the field of composite COFs as cathode materials for LIBs. Solid State Li-Ion Conducting COFs as Cathode: Solid-state lithium batteries are considered advanced EES technologies and are therefore studied extensively.[221,222]Prior research has focused on polymeric-based ion conductors[223]and inorganic sulfides-oxides.[224–226]Aside from these materials, COFs[227,228] and MOFs[229,230]with high porosity and ionic conductivity have also attracted interest in the area of solid-state batteries. Generally, the mechanism of action between solid-state electrolytes (SSE) and electrode materials in batteries involves several key processes that facilitate ion transport, charge transfer, and overall battery performance. Compared to liquid electrolytes, the diffusion energy barrier for SSE is considerably higher, as the liquid electrolyte has lower viscosity allowing for the fast exchange of ions and solvent molecules, which are not as tightly bound on a fixed lattice structure as they are in solids (Figure 8a).[224] One fundamental mechanism is ion migration through the periodic crystalline solid or chains of polymers and get stored in anode or cathode (Figure 8b).[231]In this scenario, SSE must exhibit high ionic conductivity, allowing ions (e.g., Li+,Na +,etc.) to move freely between the electrodes/SSE during charge and discharge cycles. The lattice structure and chemical composition of SSE influence ion mobility, where materials featuring open frameworks or interconnected pathways facilitate faster ion diffusion. Similar to the case with liquid electrolytes, a stable interphase layer, generally called the SEI, is formed at the electrodeelectrolyte interface. The formation and stability of the SEI layer are influenced by factors such as electrolyte composition, electrode surface chemistry, and operating conditions.[232]Additionally, the SSE/electrode interaction affects charge transfer kinetics at the electrode interface. SSE with intimate contact with Adv. Energy Mater. 2024,14, 2400521 2400521 (19 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de the electrode surface promotes rapid electron transfer between the active material and the current collector, minimizing internal resistance and voltage losses. Tailoring SSE properties, such as elastic modulus and thermal expansion coefficient, can enhance compatibility and ensure the long-term stability of the battery system.[233]In the case of using COF as an SSE, the porous and crystalline structure of COFs serves as a pathway for ion migration, allowing ions to diffuse through the framework during charge and discharge processes.[234]This ion transport mechanism is governed by the interactions between the electrolyte ions and the functional groups within the COF lattice. For instance, the presence of triazine groups within the skeleton of COF provides lone pair electrons through N atoms which attract the positively charged Li+ions.[235]This uniform distribution of triazine groups throughout the CTF structure generates conductive paths enabling fast lithium diffusion or homogeneous Li+ flux and deposition. Furthermore, the presence of 3D organized nanopores with densely packed functionalities enhances the interaction between ions and functional groups, facilitating ion hopping from one site to another (i.e., diffusion pathways) and enhancing ion mobility. The density of functional groups within these nanospaces directly influences the number of available interaction sites for ions, ultimately impacting the overall ionic conductivity. Unlike traditional inorganic or polymer solid conductors, COFs offer a unique advantage for ion transport through nanochannels, where ions hop between predefined pathways with significantly lower energy barriers.[236]COFs are endowed with an extensive free space, minimizing the energy required for ions to move,[237]in contrast to inorganic solid conductors.[224] Similarly, in polymeric solid conductors, the transfer path is influenced by the frustrated packing of linear polymers, which is heavily dependent on the degree of crystallinity and the glass transition temperature.[238]Further, COFs possess built-in pathways specifically designed to facilitate ion movement. This contrasts with polymer conductors, where the intertwined polymer chains create a complex and temperature-dependent path for ion diffusion.[239]Therefore, COFs combine the advantages of ample space and active pathways to offer superior ionic conductivity and stability for solid-state battery applications. Recently, incorporating Lewis acidic structures into porous crystalline ion conductors was proposed as a means to enhance the diffusion of Li+ions.[181,183,185]In this direction, Chen et al. introduced a solvent-free cationic COF that utilized Li salt as an ion reservoir.[181]Nevertheless, the limited interaction between the cationic framework and the free anions resulted in an inadequate supply of Li+ions (61%). On the other hand, anionic frameworks with a higher Li+content (80%) required the use of organic solvents to ensure stable ionic conductivity, albeit at the expense of undesired interfacial side reactions.[186–188]The persistence of the uncontrolled growth of Li dendrites in a solid state makes the challenge greater.[240]Hence, it becomes imperative to develop advanced single Li-ion conductors that eliminate the presence of freely mobile anions and solvents. Jeong et al. synthesized lithium sulfonated COF (TpPa@SO3Li) with the aim of establishing precisely defined ion pathways, achieving a high concentration of Li ions, and firmly anchoring anion ligands through covalent bonds.[234]Theoretical analysis unveiled the occurrence of unidirectional Li-ion transport in this material. As a result of the architecture, in combination with the absence of negatively charged mobile ions, TpPa-SO3Li exhibited phenomenal charge transport properties (ionic conductivity =2.7 ×105 Scm −1, lithium ion transference number of 0.9 at room temperature and an activation energy of 0.18 eV), without additionally incorporating lithium salts and organic solvents. Such ion transport allowed the reversible and stable lithium plating/stripping on lithium metal electrodes. An interesting aspect of most quinone-based redox compounds is the ability to receive only two electrons despite having several redox-active carbonyl groups. Truxenones, which consist of one core benzene aromatic ring fused by fluorenones have been considered that can boost the overall theoretical capacity of the electrode. For instance, Yang et al. reported COF@TRO based on truxenone as the cathodic material for solid-state LIBs.[241]The higher-density carbonyl substituents supported reversible redox reactions. This led to an excellent specific capacity of 268 mAh g−1 which is 97.5% of the projected theoretical capacity. Pristine COFs as Anode Materials for Li Ion-Batteries:Thevery first report of COF utilization in LIBs as an anode involved the use of a conjugated COF due to the high electrical conductivity and unusually high SSA, which lead to an outstanding stability and capacity.[242]Specifically, two COFs were synthesized through a condensation reaction of aldehyde and amine under solvothermal conditions. They displayed a uniform porous structure with stacking patterns. In this direction, Chen et al. reported conductive and conjugated PA-COF and TB-COF using imine linkers which delivered 401 mAh g−1and 379 mAh g−1of capacity, respectively, with excellent rate performance.[171]Both COF structures showed low charge transfer resistance, even after 500 cycles of charging discharging. In another report, Jiang et al. integrated the redox active sites of bicarbazole groups (with a pyrrole ring and conjugated aromatic carbon rings) in the pore channels of COFs to improve the specific capacity.[243]The material showed 628 mAh g−1of capacity when used as an anode for LIBs. COF structures have been also modified with carboxyl and nitride groups, which improved the overall conductivity, active redox sites, and hindered the dissolution of the active material in the electrolyte through the pi-pi interactions.[244]The presence of N═NandC═O groups was found to improve the electrochemical performance through the redox reactions/interactions. The large number of active sites, the presence of conjugated bonds, and overall geometry, surface area, and Li+transit channels, the COF anode components demonstrated improved electrochemical efficiency and morphological integrity. The respective LIBs retained 306 mAh g−1of capacity after 3000 cycles. In-situ FTIR and Raman spectroscopies showed the decrease of C═OandN═Nvibrations indicating the formation of Li-Oand Li-Nduring the charging steps (Figure 9a,b). The two-step potential change in the discharging curve verified that the binding of Li ions occurred with the COF subunit at the C═OandN═N linkages, based on the potential values of the observed steps (Figure 9c,d). The development of COF architectures with diverse sets of building units is certainly essential in identifying and optimizing chemical motives appropriate for boosting their energy storage properties. In this direction, Yu et al. developed polyoxometalate functionalized organic frameworks (CPOF), using both inorganic and organic structural components, that were joined by reversible covalent bonds.[245]The synthetic COF displayed exceptional stability, persistent porosity, and a diamondoid topology. When used Adv. Energy Mater. 2024,14, 2400521 2400521 (20 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de Figure 9. Role of chemical functionalities in storing Li+: a,b) in situ FTIR and RAMAN plot of Tp-Azo-COF during charging-discharging indicating the role of C═OandN═NinLi +storage, c) discharge curve of Tp-Azo-COF showing the number of Li+transfer at different stages (inset; FESEM image of Tp-Azo-COF), d) lithium interaction sites in Tp-Azo-COF. Reproduced with permission.[244]Copyright 2020, American Chemical Society. e,f) Structure and electrochemical performance of different COF units. Reproduced with permission.[247]Copyright 2017, John Wiley & Sons. as anode in LIBs the material exhibited 550 mAh g−1of capacity with cyclic stability of up to 500 cycles. The highly conjugated framework allowed quick electron transport and facilitated the buildup of Li+. A COF built with dehydrobenzoannulene (DBA) unit has been reported to exhibit reversible redox reactions.[246] The self-exfoliated COF (PDASA) with triazole and phloroglucinol redox-active groups was also successfully synthesized[247] and employed as a LIB anode. The COF underwent exfoliation, breaking into small nanosheets. This process shortened the diffusion pathways for lithium ions, resulting in a notable capacity of 720 mAh g−1. The high capacity was attributed to the presence of two redox-active groups capable of reversibly binding lithium ions, along with the increased redox sites following exfoliation. Upon further investigation into the charge storage mechanism, it was discovered that the short linker in the PDASA COF generated nanospaces with densely packed functionalities (as depicted in Figure 9e). In addition to this, PDASA COF contained functionalities that also enhanced the capacity retention of the material (Figure 9e,f). The functional group within PDASA acted as a Lewis acid, allowing it to form weak bonds with Li+ions. In another report, Buyukcakir et al. developed a unique rCTF COF containing triazine, benzene, and anthraquinone sites to sustain multiple redox reactions in the structure (shown in Figure 10a–c).[248]The strong triazine linkages of rCTF provided a robust polymeric framework with outstanding electrochemical durability through the creation of a conjugated framework. More readily, accessible redox-active sites are produced because of the gradual structural deformation of rCTF during activation. The anode exhibited a specific capacity of up to 1190 mAh g−1 at 0.5C at a current density of 300 mA g−1after 500 cycles. The Adv. Energy Mater. 2024,14, 2400521 2400521 (21 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de Figure 10. a,b) Different lithiation stages in rCTF COF, and c) scheme of lithiation in rCTF structure. Reproduced with permission.[248]Copyright 2020, John Wiley & Sons. presence of several functional groups and the small particle size of the COFs facilitated the Li+migration and electrolyte diffusion, leading to an astounding rate capability of over 500 mAh g−1at 20C. The charge storage mechanism was studied by DFT calculations showing the participation of the quinone linkages (1 Li+ per C═O) in the first stage of the reaction. In the second stage, Li+started to react with the nitrogen groups of the triazine rings. With the insertion of more lithium, structural changes started to take place, as highlighted in the stage 3, which generated new active sites such as C═O, C═N, C═C, and the conversion of benzene carbons to sp3hybridization. In the final stage, a subunit of the rCTF was capable of storing up to 23 Li+ions. These findings are valuable not only for the better understanding of the EES mechanism in COF-based LIB electrodes, but also to highlight the potential of such frameworks as high-performance LIB electrode materials. Recent studies have explored lithium bis- (trifluoromethanesulfonyl) imide (LiTFSI) as a solvent for the synthesis of COFs. For instance, Zhou et al. used a novel method to synthesize the CTF-1 system using LiTFSI under ionothermal conditions.[249]It was discovered that LiTFSI not only served as a promoter, but also helped to create LiF particles in situ and distribute them uniformly throughout the framework. In the context of lithium-based anodes, the hierarchical Adv. Energy Mater. 2024,14, 2400521 2400521 (22 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de framework formed by CTF-LiF on the anode surface exhibited remarkable properties. These included strong lithiophilicity, excellent interfacial stability, and a substantial lithium storage capacity. Furthermore, in addition to their redox-active properties, the presence of conjugated 𝜋–𝜋interaction sites within the structure also contributed to the storage of lithium ions. In conclusion, the limitations of pristine COFs as anode materials for LIBs, various modifications, and synthetic strategies have been employed to enhance their electrochemical performance. One approach involves functionalizing COF structures with carboxyl and nitrile groups, which not only improve conductivity but also increase the number of active redox sites and hinder the dissolution of active materials in the electrolyte through pi-pi interactions. Another method focuses on incorporating redox-active groups such as triazole, phloroglucinol, benzene, and anthraquinone into the COF backbone to enable reversible binding of lithium ions. Exfoliated COF Composites as Anode Materials for Lithium IonBatteries: COFs have the potential to serve as alternative anodes due to their composition of lightweight atoms. However, for COFs to effectively replace the commonly used graphite anodes, they need to provide a sufficient number of sites where lithium can reside within their unit cells. Exfoliating the COF material can facilitate the attachment electroactive surface groups, which, in turn, could lead to higher capacities and faster charging. Haldar et al. demonstrated how anthracene-based COFs can be chemically exfoliated into nanosheets, consisting of several layers, using maleic anhydride as a functionalizing, exfoliation and pillaring agent (Figure 11a–h).[250]The exfoliated COF provided abundant lithiophilic carbonyl functional groups, with a total Li-storage capacity of 120 atoms per unit-cell (vs one Li per C6 for the case of graphite) (Figure 11g). A full-cell device employing this COF as anode and LiCoO2as cathode delivered a specific capacity of 220 mAh g−1during a 200-cycle period. In another example of exfoliated COFs, a few-layered 2D-COF of (E-TFPBCOF) was exfoliated using a chemical stripping process and the restacking was prevented by introducing MnO2nanoparticles between the layers (Figure 11i–l).[204]The electron microscopy images of the exfoliated COF clearly showed the presence of thin films being exfoliated and decorated with MnO2. Exfoliation enabled faster ion/electron kinetics than the bulk TFPB-COF, and displayed active Li-storage sites linked to the exposed by the exfoliation conjugated aromatic moieties. After 300 cycles, the ETFPB-COF/MnO2and E-TFPB-COF electrodes displayed superior and reversible capacities of 1359 and 968 mAh g−1,respectively (Figure 11m). In situ Raman and FTIR spectroscopies for the exfoliated and the bulk COF it was found that Li+was interacting with the C═C groups in the conjugated C6 rings, the C═N groups, and with the Mn-O groups (Figure 11n–q). It was also observed a reduced amount of sp2carbons in Raman, indicating the interaction of Li+with benzene rings. In the case of the bulk COF, the C═N groups were found to interact with Li+whereas C═C and benzene groups were found to be mainly inactive toward Li storage. In a different approach, well-distributed Co3O4nanoparticles on N-doped porous carbon were obtained from the carbonization of a MOF/COF composite.[251]In particular, the ZIF-67/COF hybrid was produced by growing ZIF-67 microcrystals in the presence of benzoic acid-modified COF units. The final Co3O4/NPC composite was synthesized after the calcination of ZIF-67/COF. The fine dispersion of Co3O4nanoparticles was achieved due to the interactions developed with the benzoic acid groups which were present on the starting COF. Due to the COF’s porosity, the produced Co3O4/NPC exhibited an SSA of 228.0 m2g−1,and when tested as an anode for LIBs it delivered 785 mAh g−1of specific capacitance at 500 mA g−1. DFT calculations showed that the exceptional morphology and electronic band structure of Co3O4/NPC, and improved the adsorption/desorption of electrolytes and ions and accelerated electron transport. Table 1 shows the comparison of different COF materials as anode and cathode for Lithium batteries. 6.1.2. COFs for Na/K-Ion batteries To meet the increasing need for sustainable and cost-effective EES technologies, concerted efforts are focused on investigating alternative energy storage chemistries beyond lithium-ion batteries, as a way to circumvent the limited lithium resources. Consequently, there is a growing interest for the adoption of new alkaline-ion batteries, involving elements like Na and K. Currently, organic electrode materials face several challenges when it comes to their use in Na/K-ion batteries.[252–255]Consequently, the design and development of new organic electrode materials to enhance their efficiency in the respective chemistries is of paramount importance. In this section, the latest developments in the application of structural frameworks related to COFs for Na/K-ion batteries (NIBs/PIBs) are discussed. COFs for Na-Ion Battery Applications: NIBs are a promising chemistry for energy storage, due to their similar chemistry to LIBs (thus compatible with current production methodologies), abundance in nature, and economic benefits. The reaction potential of Na (−2.71V) is remarkably close to the reaction potential of Li (−3.04 V). However, SIBs have much lower energy densities and cycle stability than LIBs, due to the bigger radius than Li that causes significant volume changes in the electrode materials throughout the charge-discharge process. The continuous volume changes during charging/discharging create voids in the material and lead to the loss of conductive pathways. Commercial graphite anode is incompatible with SIBs due to the larger Na+ions which do not intercalate into the graphite layers. In the pursuit of developing COF-based electrodes for SIBs, Park et al. demonstrated that few-layered COF nanosheets could display large charge-carrier conductivity by securing the planarity of the polymer framework backbone and by increasing the SSA, eventually leading to high Na-ion storage capacities.[256]By using different monomer combination to build COF, the macromolecular ring diameter has been tuned from 2.8 to 4.2 nm. The sample prepared with solvothermal method and having 2.8 nm of ring diameter showed 250 mAh g−1of capacity for 30 cycles at 100 mA g−1,whenusedasananodeforSIBs.Liu et al. produced crystalline, layered, millimeter-sized CTF COF through liquid sonication and mechanical exfoliation process for NIBs.[257]The obtained CTF displayed an AB stacking motif with 0.6 nm of pore size, which is unique compared to AA stacking found commonly in COFs. Computational studies demonstrated that the specific interaction of triflic acid molecules with CTFs contributed to the AB stacking. The nanosheets of CTF Adv. Energy Mater. 2024,14, 2400521 2400521 (23 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de Figure 11. Exfoliation strategy for COFs: a,b) exfoliation of IISERP-COF-7 and IISERP-COF-8 COFs through their functionalization with maleic anhydride, c) TEM images of COFs before and after exfoliation, d) cell assembling utilizing the COFs as anodes, e) charge–discharge of IISERP-CON-2, f,g) rate performance and Li+interaction sites in the exfoliated COFs, h) capacity retention of the COFs and other materials (reproduced with permission,[250] Copyright 2019, John Wiley & Sons), i) exfoliation of TFPB-COF by inserting MnO2nanoparticles, j–l) TEM image of the exfoliated COF, m) cycling performance of different COFs, and n,o) in-situ Raman and FTIR for the exfoliated COFs and p,q) for bulk COF (reproduced with permission,[204] Copyright 2019, John Wiley & Sons). experienced only a 5% capacity loss over 1200 cycles retaining 198 mAh g−1of the initial capacity. Apart from this, increasing the porosity of the material further enabled improved diffusion paths for Na+in the host material. In this direction, Patra et al. produced a novel micro-spherical COF structure (TFPBTAPT COF) with an opened and ordered nanoporous framework. The COF showed extended cycle stability and initial reversible capacity (246 mAh g−1) with a diffusion coefficient of 6.275 ×10−15 cm2s−1.[258]The interlayer distance of (002) plane is ≈3.4 Å, which is suitable for ion insertion in the TFPB-TAPT COF. During ion insertion/extraction, there is an increase in the interlayer distance (3.4–3.8 Å), which is observed in in-situ XRD where the peak position shifted from 25.8°to ≈22°.From the HRTEM analysis, the reversible structural changes have also been observed at different charging–discharging voltages. Jagt et al. synthesized four PI-based COFs by combining aromatic triamines with aromatic dianhydrides.[259]DFT calculations illustrated the preferred assembly of imide linkages in an eclipsed perpendicular stacking, thereby breaking the 2D symmetry and shrinking the channel diameter, while also expanding the pore wall thickness. At a working potential over 1.5 V vs Na/Na+, these specific geometric shapes provided a framework for Na+intercalation and stable cycle life. The nitrogen on the amine linkages provided greater rotational flexibility which made torsion significantly more durable in COF structures with the TAPA connecting molecule. On the other hand, a study found that the integration of redox-active quinones in COFs through linkers significantly enhances their electrochemical performance when applied Adv. Energy Mater. 2024,14, 2400521 2400521 (24 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de Table 1. Electrochemical performance comparison of different COF structures and its composites for Lithium Batteries. Electrode Material Electrolyte Potential vs Li/Li+[V] CC/DC/R Cyclic stability RC/R/CN Refs. Cathode Tp-DANT/COF 1 m LiPF6in DMC/EC/EMC 1.5–4.0 78.9,93.4,200 92.3/200/200 [196] Cathode Tb-DANT/COF 1 m LiPF6in DMC/EC/EMC 1.5–4.0 135.4/144.4/50 80.1/200/300 Cathode DAAQ-ECOF 1 m LiTFSI in TEGDME 1.5–4.0 -/145/20 104/500/1800 [197] Cathode PCT-1 1 m LiPF6in EC/DEC 1.75–3.0 -/288/500 – [198] Cathode PIBN-G 1 m LiTFSI in DOL and DME 1.5–3.5 -/271/0.1C 271/0.1C/300 [201] Cathode E CIN-1/CNT 1 m LiPF6in EC/DEC 0.001–3.0 520/1269/100 744/100/250 [203] Cathode BQ1-COF 1 m LiTFSI in DOL/ DME 1.2–3.5 -/321/390 158/3870/1500 [174] Cathode F-CQN-1-600 1.2 m LiPF6 in EC/EMC 1.5–4.5 -/250/100 120/2000/2000 [205] Cathode 2D PAI@CNT 1 m LiTFSI in DOL/ DME 1.5–3.5V – 104.4/100 [168] Cathode CTF/rGO 1 m LiPF6 in EC/DEC 1.5–4.5 -/235/100 – [209] Cathode PIX/rGO 1 m LiTFSI in DOL/DME 1.5–3.4 -/172/500 – [215] Cathode IEP-11 1 m LiTFSI in DOL/DME 1.5–3.5 -/147/149 – [216] Cathode AQ-COF@CNT 1 m LiTFSI in TEGDME 1.5–3.5 -/144/50 131/500/3000 [218] Cathode Pyr-2D COF 1 m LiPF6in EC/DEC 2.8/4.5 -/210.1/600 – [220] Cathode COF-TRO 11 m LiPF6in EC/DEC 0.5–4.5 */268/0.1C [241] Anode PA-COF 1 m LiPF6in EC/DEC/DMC 0.01–3.5 267/321.9/1000 401.3/100/500 [171] Anode TB-COF 1 m LiPF6in EC/DEC/DMC 0.01–3.5 262.4/311.4/1000 379.1/100/500 Anode Cz-COF1 1 m LiPF60.005–3.0 -/628/100 236/200/400 [243] Anode JUC-526 1 m LiPF6in EC/DEC 0.01–3.0 509.6/750.6/50 503.3/100/500 [245] Anode DBA-COF 3 1 m LiPF6in EC/DMC 2.0–4.0 -/522/50 207/50/90 [246] Anode rCTF 1 m LiPF6in EC/DEC 0.005–3.0 -/1750/300 1190/300/1000 [248] Anode IISERP-CON1 1 m LiPF6in EC/DMC 0.01–3.0 -/2060/100 720/100/100 [247] Anode IISERP-CON2 1 m LiPF6in EC/DMC – -/790/100 – [250] Anode E-TFPB-COF 1 m LiPF6in EC/DEC 0.005–3.0 1211/-/100 968/100/300 [204] Anode E-TFPB-COF/MnO21mLiPF 6in EC/DEC 0.005–3.0 1274/2423/100 1359/100/300 Abbreviations: LiTFSIlithium bis(trifluoromethanesulfonyl)imide, DOL1,3-dioxolane DMEdimethoxyethane, DMCdimethyl carbonate, ECethylene carbonate, DEC-diethyl carbonate, TEGDMEtetraethylene glycol dimethyl ether, EMC-ethyl methyl carbonate, CC-charge capacity (mAh g−1), DC-discharge capacity (mAh g−1), R-Rate (mA g−1), RCReversible capacity (mAh g−1), CNCycle number. as electrodes. These COFs are stable preventing the dissolution of quinones in the organic electrolytes, while their ordered, porous structures facilitate ion diffusion. Enhancing these frameworks with linkers that contain additional replaceable sites further amplifies the redox-active components in COF electrodes, thereby boosting their specific capacities. A COF was synthesized by condensing 2,6-diaminoanthraquinone (DAAQ) with hexachlorocyclotriphosphazene (HCCP), a linker endowed with six replaceable chlorine sites, resulting in an ordered porous DAAQ-HCCP COF.[260]During the condensation process, all chlorine sites in the HCCP linker were substituted with the redox-active DAAQ molecules, markedly enriching the framework’s content of electroactive groups. The resultant DAAQ-HCCP COF outperformed DAAQ in terms of cycling stability and exhibited superior rate performance as an anode in SIBs. The COF demonstrated specific capacities of 88 mAh g−1at 100 mA g−1after 100 cycles and maintained 72 mAh g−1at 2 A g−1after 1000 cycles. The dissolution of active materials in NIBs is known to be a severe limitation that restricts stability. On this basis, Ha et al. reported the mitigation of active material dissolution in electrolytes and increased electron mobility of organic electrodes by esterifying 2,5-dihydroxyterephtalic acid (DHTPA) into carbon black (CB).[261]The sample DHTPA/CB showed outstanding rate capabilities and maintained 90% of its initial capacitance after 100 cycles. The coulombic efficiency during the initial cycle was approximately 74.2%, which was ascribed to the irreversible decomposition of the electrolyte leading to the formation of a SEI. Additionally, the detachment of the weakly-grafted DHTPA onto the CB surfaces contributed to this phenomenon. The storage of Na can also be enhanced by incorporating functional groups that can Adv. Energy Mater. 2024,14, 2400521 2400521 (25 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de network on the surface of CNTs can be constructed using an appropriate organic condensation polymerization architecture. The COF precursor’s homogeneous distribution of boron and oxygen heteroatoms was crucial for enabling uniform doping of carbonbased materials. The BOC@CNT with 68.5 wt.% sulfur exhibited superior LiPS absorptivity and electrochemical characteristics as a cathode for Li-S batteries, resulting into enhanced reversible capacitance (1077 mAh g−1) and outstanding cycle life (794 mAh g−1). To improve the cycling stability in Li-S batteries, Wang et al. produced an imine-linked material, TAPB-PD@COF (where TAPD stands for 1, 3, 5-tris (4-aminophenyl) benzene and PDA for terephthaldehyde) and utilized it for sulfur loading.[290] The host material could retain 60 wt.% sulphur. The COF structure possessed a beehive-like architecture with high thermal stability (up to 500 °C). Conductivity enhancers of acetylene black (A-B) and super-P (S-P) were employed to improve the electron transport in the material. TAPB-PDA-COF/S@A-B and TAPBPDA-COF/S@S-P had initial discharge capacities of 991 mAh g−1 and 1357 mAh g−1, respectively, due to the higher conductivity of S-P in comparison to the A-B additive. When the current density was increased to 2 A g−1, the S-P reinforced cathode materials delivered an initial discharge capacity of 630 mAh and 274mAh g−1 after 940cycles. To engineer efficient Li–S batteries, it is also necessary to explore alternative ways to boost the performance through the seamless integration of conductive additives due to the insulating nature of sulfur and mitigate the trade-off between high capacity (i.e., high sulfur loading) and reduction in conductivity. For example, Li-S batteries can exploit MXenes, a class of electroactive and conducting materials, as conducting additives in the cathode’s host matrix. However, MXenes exhibit poor wettability in organic solvents and interaction with lithium ions. 2D COFs, on the other hand, display considerable surface area promoting sulfur immobilization. Therefore, the combination of MXenes with COFs can bring exciting synergistic effects. In line with this strategy, a stacked covalent triazine scaffold was grown on top of Ti3C2 MXene nanosheets (CTF/TNS) and tested for LiS batteries.[291] The composite material showed improved kinetics while retaining substantial sulfur and exhibiting fast electron/ion transport. Due to the lithiophilic N sites in CTF and sulfurophilic Ti sites in the MXene structure, polysulfides could bind strongly. The S@CTF/TNS cathode showed a high reversible capacity of 1441 mAh g−1at 0.2 C in addition to outstanding rate and exceptional cycling durability (up to 1000 cycles at 1 C with 0.014% capacity loss per cycle). After 100 cycles, even with a large sulfur loading of 5.6 mg cm−2, 94% of the initial capacity was retained. The triazine ring with abundant N atoms and imine linkages was critical for the overall stability of the COF hybrid structure. The presence of C═N bonds also exerted electrostatic repulsion forces increasing the interlayer spacing, which was crucial for creating fast Stransport channels. In summary, the presence of conjugated moieties and electronegative groups in the material’s framework are beneficial for the adsorption of LiPSx, whereas the crystallinity and porous structure of COFs provide fast Li+and S-transport channels. Although conductivity issues are currently tackled through the use of conductive additives, their, usually, low Li-ion storage capacity remains an issue. For this reason, the development of porous, rigid, and intrinsically conductive COFs which can host large amounts of sulfur keeping ultrafast electron transport is highly required. 6.2. COFs for Other Batteries Previously, we reviewed COFs which are widely explored in LIBs and LSBs. There are also several reports exploring the use of COFs as electrodes for Na/K-ion batteries (NIBs/PIBs). Besides, researchers are also shifting their interest in other battery chemistries like metal-oxygen batteries, and multivalent ion batteries, such as Zn-ion batteries (ZIBs). In this sub-section, we review these categories of batteries where COFs have been less intensively explored, but have the potential to attract widespread attention in near future. Banerjee et al. created a 𝛽-ketoenamine COF (HqTp-COF) for ZIBs cathodes for the first time.[292]The primary constituents for Zn2+storage are the C2 symmetric C═O group produced by the electrochemical oxidation of the hydroquinone linkage unit and the C3 symmetric C═O group produced by the conversion of enol to keto tautomerism. Excellent discharge capacity for HqTpCOF is provided by the reversible interlayer interaction of Zn2+ with the C═O groups of the neighboring layers. At 125 mA g−1, it demonstrated a specific capacity of 276 mAh g−1, and it retained the initial capacity of 95% after 1000cycles. Following that, Liu et al. designed Tp-PTO-COF employing 2,7-diaminopyrene4,5,9,10-tetrone (PTO) and 1,3,5-triformylphloroalucinol (Tp) in order to further improve electrochemical performance of the ZIB cathode.[293]Zn2+is stored in the double-active sites of the 𝛽-keto carbonyl and neighboring carbonyl acting as nucleophilic centers. Tp-PTO-COF employs an ionic coordination mechanism to store charges. To be more precise, during the electrochemical reduction of carbonyl groups, each Zn2+is coordinated to two negatively charged oxygen atoms in the interlayers and reversibly delocalized during the charging process. Consequently, the TpPTO-COF achieved a reversible capacity of 301 mAh g−1at 0.2 Ag −1. In another report, Li et al. designed a TA-PTO-COF generated by covalently bonding tris(4-formylbiphenyl)amine (TA) and PTO-NH2for ZIB cathode application.[294]The electron delocalization and intermolecular interaction were amplified with the highly conjugated skeleton, resulting in high electronic conductivity. TA-PTO-COF cathode delivered a capacity of 255 mAh g−1 at 0.1 A g−1along with a promising rate capability of 186 mAh g−1 at 10 A g−1. The reactive sites such as C═O, C═N, and charge transport pathways (i.e., the open channels present within the TA-PTO-COF) were deemed responsible for the exceptional performance. Several intrinsic limitations in conventional zinc metal anodes like dendrites development, parasitic reactions, research also focuses on developing smart solutions for improving the plating of the metal on the anode. Thus, the development of zinc anode protective layers and the pursuit of novel anode materials are essential components in promoting the performance and safety of ZIBs. Yu et al. synthesized a two-dimensional polyarylimide covalent organic framework (PI-COF) by mixing with CNTs, TAPA and NTCDA, which was used as an anode for Zn2+storage.[295] The ordered pore network of PI-COF allowed the effective diffusion and interaction of the zinc ions with the built-in redox-active carbonyl groups. Experimental and theoretical data indicated a Adv. Energy Mater. 2024,14, 2400521 2400521 (32 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de two-step Zn2+-storage mechanism, in which the carbonyl groups reversibly formed negatively charged enolates. Thus, the PI-COF anode exhibited a specific capacity of 92 mAh g−1at 0.7 A g−1,a high rate capability (79.8% at 7 A g−1), and a long cycle life (85% over 4000 cycles). By increasing the exposed Zn anode surface, the development of zinc dendrites amplifies the side reactions, such as hydrogen evolution reactions and corrosion. In addition, the device impedance increases deteriorating further ZIB capacity.[296–298] The dendritic nucleation sites hamper the smooth plating and striping of zinc metal that eventually result in a short circuit and battery failure.[299]As a result, scientists have developed a number of strategies, such as constructing scaffolds or nucleation layers, improving electrolytes SEI formation with additives, or developing surface-protective layers.[300–302]COFs have thus been utilized for the modification of the interfacial interactions between the electrolyte and the electrode materials and inhibition of dendrite formation by promoting the uniform deposition of metal ions during stripping/electroplating.[298]Owing to their high surface area, COFs can efficiently manage the spatial electric field and distribution of Zn2+flow, slowing down H2production and decreasing the energy barriers of zinc deposition.[303]The synthesis of a large-area COF film by condensation of 1,3,5-tri-formylphloroglucinol (TFP) and different aromatic amines was demonstrated by Grzybowski et al. using a dip-coating technique.[304]This efficiently prevented dendritic development and surface-side reactions after the self-assembly of the COF on the anode current collector. Such COF-protective thin films resulted in stable ZIB cycling for 420 h at 1 mA cm−2 without compromising Coulombic efficiency and showed a significant improvement compared to the ≈40 h of stable cycling for the bare Zn anode. To develop a zinc anode devoid of dendrite formation, Wang et al. studied a porous CTF as a zinc protective layer.[305]By cooperatively coordinating with Zn2+, the nitrogenrich sites in CTF efficiently reduced the Zn2+concentration gradient and nucleation overpotential while promoting Zn nucleation. Furthermore, while controlling the Zn2+diffusion process, the CTF coating secured the uniform Zn deposition, prevented side reactions by isolating the Zn anode from the electrolyte. Thus, a Zn//Zn symmetric cell using the CTF-protected anode achieved stable operation for 7000 h. Guo et al. used a hydrothermal method to directly metalize COFs with Zn(CH3COO)2in order to better explain the effect of various components on inhibiting HER and dendrite growth.[306]They synthesized Zn-AAnCOF, Zn-DAA-COF, and Zn-DAAQ-COF as model platforms to control Zn2+flux and H2evolution in zinc-air batteries (ZABs). Zn-AAn-COF was used as an effective model platform for ZABs study because of its high porosity, many Zn nucleation sites, and zincophilic groups (such as C═OandC═N). The inhibition of HER on the electrode based on the Zn-AAn-COF was established both theoretically and empirically. By pouring a COF-based polyvinyl chloride (PVC) suspension over the zinc plate (PVC-ZnAAn-COF@Zn), the electrodes were protected by the COF layer. A control experiment with an unprotected zinc anode showed that after 10 cycles protrusions and nucleations on the zinc foil were visible, and as the number of cycles increased they progressively transformed into zinc dendrites. Significant corrosion, large H2bubbles, and highly disordered Zn deposition were observed after 100 cycles on the bare Zn foil surface. On the PVCZn-AAn-COF@Zn protected foil, however, homogeneous thick Zn deposits were observed after 100 cycles under identical conditions, without any indications of H2bubbles or development of dendrites. The unique chemical groups in COFs can develop specific interactions with oxygen from the air during the operation of metal-oxygen batteries. Recently, functionalized COFs have also explored for zinc–air batteries with promising results. For instance, Cao et al. demonstrated the use of fluorinated COF.[307] To improve the affinity of O2in the cathode electrode, the authors used fluorinated alkyl chains decorating the COF structure with hydrophilic NiFe layered-double-hydroxide as an electrocatalyst. With the help of the COF porous structure, it was possible to segregate the water and O2at the nanoscale which greatly enhanced themigrationofO 2within the cathode. Furthermore, Zhang et al. employed a composite made of porphyrin COF and CNT (POF@CNT) as the cathode in liquid as well as flexible all-solidstate zinc-air batteries.[308]The all-solid-state battery had a high energy efficiency (61.6% at 1.0 mA cm−2), while the liquid Znair battery showed good stability (200 cycles) and a narrow voltage gap (0.71 V). Considering the intricate chemistry in metal– air batteries rendering stable cycling very challenging, the Zn– air battery’s outstanding performance was ascribed to the complementary actions of CNT and porphyrin COF (POF). The hydrophilic surface and well-defined cobalt-coordinated porphyrin active sites supplied by POF were complemented by the various electron routes and enhanced electron transport that were provided by interwoven CNTs. COF materials are gaining recognition for their potential to curb the migration of active materials in various other battery types. For instance, very recently, Zhang et al. used exfoliated COF structure as a cathode to hold bromine (Br) for Zn–Br batteries.[309]The abundant functional groups in COF provided the adsorption sites for polybromide whereas the same COF layer over the Zn anode regulated the Zn flux to reduce the production of dendrites. The full cell delivered the 183 mAh g−1of capacity after 1000 cycles with capacity retention of 83% at 2 A g−1. In another study, Khayum M et al. used 𝛽-ketonamine COF coupled to hydroquinone for the first time, functioning as a Zn2+anchor in an aqueous rechargeable zinc ion battery (ZIB).[292]Efficient reversible interlayer interaction between Zn2+ions and the functional moieties in the neighboring COF layers accounts for the charge storage mechanism. Notably, a built-in complete cell exhibits a discharge capacity as high as 276 mAh g−1at a current rate of 125 mA g−1because of the well-defined nanopores and structural structure. Beyond ZIBs, magnesium ion batteries (MIBs) and calcium ion batteries (CIBs) show great promise for large-scale energy storage due to their low cost, abundance, and exceptional safety in ambient environments. COFs are promising cathode materials for these batteries owing to its intriguing properties. However, research in this field is still nascent stage and only few reports are published till now. For instance, Sun et al. reported COF as cathode for the rechargeable MIB.[310]It shows a high-power density of 2.8 kW kg−1, and a high specific energy density of 146 Wh kg−1along with extraordinary cycle life. This demonstrates that the ultrafast reaction kinetics are mostly explained by pseudocapacitive behavior, and the triazine ring sites in the COF are redox centers for reversible interaction with magnesium ions. Zhang et al. proposed TB-COF based on triquinoxalinylene and Adv. Energy Mater. 2024,14, 2400521 2400521 (33 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de benzoquinone units as anode for high-performance aqueous CIB.[311]In TB-COF, ion and electron transport are facilitated by the abundance of active sites and the 𝜋-conjugated structure. It therefore provides excellent rate performance (104 mAh g−1at 70 Ag −1) and a large reversible capacity (253 mAh g−1at 1.0 A g−1). Thanks to its insoluble nature and stable structure, TB-COF has a long cycle life, with capacity loss of 0.01% per cycle at 5 A g−1 after 3000 cycles. Following three intercalation stages, which include three different types of Ca2+ion storage sites, a maximum of nine Ca2+ions may be stored per TB-COF repeating unit. Besides, divalent metal ion batteries, trivalent ion (Al3+) based batteries also attracted researchers’ attention in recent times. COFs can show promising performance when utilized as an electrode for Al ion batteries (AIB). For instance, Lu et al. reported a 2,2’-bipyridine moieties-based COF as cathode material in AIB.[312]Because of their strong frameworks and hierarchical pores with a large specific surface area, the COFs allow rapid anion diffusion and intercalation without structural collapse, which is verified by both theoretical and experimental studies. After 13 000 cycles at 2 A g−1, the resulting AIB shows exceptional long-term stability, with a reversible discharge capacity of 150 mAh g−1. Additionally, it has a remarkable rate capability of 113 mAh g−1at 5 A g−1. Similarly, Liu et al. reported two PIs based 2D COFs cathodes with redox-bipolar capacity in rechargeable AIB.[313]The porous polymer skeleton of 2D-COFs incorporated the active centers of n-type imide and p-type triazine which is responsible for effective charge transfer. The ideal 2D-COF electrode reached a high specific capacity of 132 mAh g−1. Nonetheless, the available literature on COF applications in dual-ion batteries remains scarce, leaving ample room for further exploration and research in this domain. 6.3. COFs as Separators and Coatings in Batteries The application of COFs is not only limited to the cathodic and anodic materials but it is also extended to the generation of protective layers for electrode materials and separation membranes. This is due to their high porosity, flexible nature, and most importantly electrically insulating but ionically permeable nature that COFs can provide through appropriate synthetic design. Xu et al. proposed a redox-active COF as a separator for Li–S batteries,[314] whereby the 1D pore channels of COF assisted for Li+transport and the pyridine subunits of the framework facilitates sulfate adsorption. The material delivered a specific capacity of 977 mAh g−1at 0.2 C after 100 cycles, a value that was 5.2 times higher than the respective values observed using the same electrode materials but with glass or cellulose as separators. Wang et al. developed a straightforward technology based on a coated functional separator forming a network by combining COFs with CNTs, which was not permeable to the dissolved polysulfides (COF-CNT-separator).[315]With an 80% sulfur concentration in the cathode, the cell retained a considerably high capacity of 1068 mAh g−1at 1 A g−1after 500 cycles. Straightforward methods based on the integration and network formation for developing separators is a promising strategy for the assembly of highly efficient Li-S batteries. In such an example, ionic covalent organic nanosheets (iCON) based on guanidinium were deposited over Ti3C2MXenes to form a coating layer on the polypropylene separator.[316]This modification suppressed the shuttle effect of polysulfides by efficiently intercepting their diffusion, accelerated the redox kinetics of sulfur species, and promoted efficient conversion of intercepted polysulfides owing to the synergistic effects from Ti3C2and iCON. Particularly, this was attributed to the dynamic adsorption of polysulfides at the Ti3C2@iCON-PP separator and their subsequent catalytic conversion. The electrochemical efficiency of carbon nanotube/sulfur cathodes was significantly enhanced through the use of such functionalized separators, leading to an average capacity decay per cycle over 2000 cycles at 2 C only by 0.006%, keeping 706 mAh g−1of the initial specific capacity of 810 mAh g−1. At 0.05 C, the battery achieved an initial discharge capacity of 1417 mAh g−1, corresponding to 85% of the theoretical capacity of sulfur. Even at a 5C rate the discharging capacity was 687 mAh g−1, while at a commercially relevant electrode mass loading of 7.6 mg cm−2, the cell still delivered a high initial capacity of 1186 mAh g−1. Another common issue encountered during battery operation is the rise of internal resistance with working cycles. This is often due to the dissolution of metal oxides in the electrolyte and the subsequent deposition of oxides at the anode. The inadequacy of the traditional separators to control the metal oxides’ diffusion from the cathode to the anode is typically the reason behind this phenomenon. To decrease the impact of such processes, a highgrade separator can be used, because it has very small pores that can only let Li+to pass through. However, using such separators is very costly, drastically decreasing the advantages that they aim to bring. Therefore, modern LIBs using transition metal oxide cathodes require separators that are extremely permeable for Li+ and cheap, but also non-conductive for transition metal ions. In this context, Wen et al. proposed a new polymer separator that can control both Li+and transition metal ion mobility.[317]It was produced by laminating a COF based on 2,5-dimethoxybenzene1,4-dialdehyde and 1,3,5-tris(4-aminophenyl) benzene on an industrial polymer separator. Electrochemical measurements and physical characterization demonstrate that the lithium-ion transference number of this separator was two times that of the uncoated one, and successfully intercepted the soluble transition metal ions from the cathode before reaching the anode half-cell. Therefore, the performance stability during cycling and rate capability. were significantly improved. Lightweight membranes of under 10 microns are of particular interest in batteries architecture because their deployment may increase the energy density. It is extremely challenging to produce such fine membranes using traditional nanofabrication methods. In one report, a 7.1 μm thin hetero-layered Kevlar/COF composite membrane was developed using a bottom-up layerby-layer method (Figure 17a–e)[318]that allowed for precise control over the structure and thickness of the membrane. The weak 𝜋-𝜋stacking of the guanidinium-based cationic COF was confirmed from XRD which then was ultrasonically exfoliated to obtain single-layer COF sheets (Figure 17b–d). The 2D COF sheets are tightly interlocked with the Kevlar units via electrostatic coupling, enabling quick Li+transfer (Figure 17e). The developed membrane showed high Li+conductivity (1.6 ×104Scm −1at 30 °C) which allowed the operation of an all-solid-state lithium battery with an improved energy density, that could prevent shortcircuiting even after 500 hours of cycling. When used in a full cell of LIBs, the battery exhibited excellent rate performance with Adv. Energy Mater. 2024,14, 2400521 2400521 (34 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de Figure 17. a) Schematic of assembling a 7.1 μm thick heterolayered Kevlar/COF composite membrane (inset: 500-bilayer L@K/C membrane), b) COF structure, c) XRD of COF, d) TEM and AFM profile of COF film, e) cross-linking Kevlar with PEG polymer, f) SEM of L@K/C membrane, g) electrochemical performance of assembled cell (LFP/L@K/C/Li), and h) Gravimetric and volumetric energy densities of cell with different membrane. Reproduced with permission.[318]Copyright 2020, American Chemical Society. high energy density of almost 250 Wh kg−1(Figure 17g,h). Similarly, Zhang et al. demonstrated that a fluorine COF (F-COF) based nanofluidic and negatively charged membrane was capable to improve the shuttling effect in Li-S batteries.[319]The highly ordered and negatively charged membrane (−46.7 mV) acted as a permselective barrier that allowed the Li+diffusion but limited the migration of LiPSs. With the use of 4F-COF membrane only 0.018% capacity fading per cycle was achieved. Under the same conditions, a COF membrane with less negative charge (−28.9 mV) failed after 520 h of operation. It was observed that already after 10 h, the electrolyte color changed, indicating the migration of LiPSs to the electrolyte. The control of the porosity of the cathode and the catalytic properties for the sulfur reactions can provide a significant improvement of the overall performance of the Li–S batteries. For instance, Wang et al. demonstrated the use of TpPa-1 COF cobaltdecorated titanium oxynitride (TiOxNy) as a cathode material for LiS batteries.[320]The presence of the COF layer reduced the migration of LiPSs, whereas the cobalt atoms acted as a catalytic site for sulfur reactions. Furthermore, the oxygen deficiency and macropores present in the oxide framework retained the flow of electrons as well as the high loading of sulfur. The cathode underwent a 0.031% of capacity fade per cycle for 500 cycles at 1C rate, while the pouch cell retained 554.5 mAh g−1of capacity at 0.1 C after 50 cycles. COF-based solutions have been also developed to tackle the unfavorable dendrite growth and inefficient Li consumption in lithium metal batteries which has so far limited the widespread Adv. Energy Mater. 2024,14, 2400521 2400521 (35 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de Figure 18. a) Schematic of CTF synthesis starting from the precursor dicyanobenzene, b) coating of CTF-LiI over lithium foil, c) schematic of the effect of CTF coating over the Li anode for smooth lithium deposition, d) CTF-LiI solution, e) prepared CTF-LiI film, f) bending test of film, g,h) SEM of CTF-LiI over lithium foil, i) lithium anode SEM after 20 cycles, and j) CTF-LiI coated lithium anode SEM after 20 cycles, k) rate performance of different anode, l) Nyquist plot for anode before cycling, m) Nyquist plot for anode after cycling, n) cycling performance of different anode. Reproduced with permission.[235]Copyright 2020, John Wiley & Sons. Li–metal batteries.[321]To address this, Xu et al. developed COF-LZU1 as a protective layer between the Li-anode and the separator.[322]The COF was synthesized by the reaction between 1,3,5-triformylbenzene and 1,4-diaminobenzene. TFSI anions (bis(trifluoromethanesulonyl)imide anions) were immobilized on COF-LZU1 by interactions with the aldehyde functional groups, reducing the impact of space charge (typically achieved by reducing the anion mobility) and hence limiting dendrite growth. The imine-linked COF-LZU1 was also lithophilic, which enabled a homogenous distribution and transport of lithium ions. This homogeneity in ion flux distribution further contributed in reducing space charge effects and resulted in lower voltage hysteresis during battery operation, and hence further limiting dendritic proliferation. With the assistance of the COFLZU1 protective layer, Li metal was smoothly and densely deposited onto the anode, while dendritic Li deposition occurred on a bare Cu electrode. The anode surface of COF-LZU1-modified cells remained dense and smooth even after several cycles, which contributed to improved lithium utilization and cyclability, leading to high coulombic efficiency and reversible rate capacity. The dendrite-free anode demonstrated 99% Li utilization and a cycle life of up to 2000 h. Furthermore, Li–S batteries containing COF-LZU1 layers also showed better rate performance and cyclic stability. In contrast, bare lithium symmetric cells operated effectively for <750 h. In another report, a flexible and conformal CTFLiI coating was coated on metallic Li anode (Figure 18a,b).[235] The bendable and foldable CTF-LiI coating minimized parasitic reactions between metallic Li and the electrolyte while rendering the Li electrodeposition uniform, and dendrite-free (Figure 18c–f). Upon charging–discharging, the assembled cells with bare Li and CTF-LiI-coated anodes, significant Li dendrites were grown only in the case of the uncoated anode (Figure 18g,h). Furthermore, EIS analysis after cycling, showed that the CTF-LiI coated Li anode retained a very low charge transfer resistance. The observed behavior and the reduction of dendrite growth were assigned particularly to the high lithiophillicity brought by LiI and the protective layer of CTF (Figure 18 l,m). The Li symmetric batteries exhibited an impressively low voltage fluctuation with stable operation for 2500 cycles at 10 mA cm−2. The capacity of the cell with bare Li dropped to almost 450 mAh g−1from 1150 mAh g−1after 120 cycles, whereas the cell with CTF-LiI coating retained more than 1000 mAh g−1of capacity (Figure 18k). The production of ultrathin and rigid COF films remains a significant challenge due to the powdered nature of COFs. To resolve this issue, Bian et al. produced stable ultrathin COF films by using a side-chain engineering strategy to weaken the Adv. Energy Mater. 2024,14, 2400521 2400521 (36 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de interlayer interactions in the COF structure.[323]The produced COF–C16/PE composite membrane (≈9μm thick) retained high chemical and mechanical stability. The membrane was tested in Li–LiFePO4, Li-S, and quasi-solid batteries. In the case of Li– LiFePO4batteries, the device remained stable up to 850 cycles with 128 mAh g−1of capacity. 7. COFs as Supercapacitors Supercapacitors possess distinctive characteristics, including a high-power density, extended cycle lifespan, excellent costefficiency, and a broad operational voltage range. Thus far, two distinct approaches have been recognized for the energy storage mechanism of supercapacitors. Energy storage through faradaic processes[324,325]pertains to the reversible redox reactions of electrode materials (pseudocapacitance), in contrast to non-Faradaic processes[326]where ion adsorption occurs on the electrochemical double layer (double layer capacitance). Effective ion adsorption requires a large surface area and readily accessible pores.[327,328]Therefore, it is considered that among the best materials for developing supercapacitor electrodes are those with high surface areas, accessible pore networks, conductivity, and reversible redox-activity.[329,330]COFs fulfill such criteria very efficiently.[331]Furthermore, 2D COF architectures facilitate bidirectional electrochemical processes and can include functional linker moieties ascribing redox activity. For instance, An et al. fabricated an anthraquinone-based 2D COFs/graphene composite aerogel (DAAQ-COFs/GA) electrode which delivered a superior and long-term cycling stability with a capacitance of 380 F g−1in 1 m electrolyte and high retention of 87.8% after 20 000 cycles.[332]Li et al. developed a 2D conductive Ni-COF with square-planar Ni(II) coordination centers[333] by reacting 1,2,4,5-benzenetetraamine and 2,5-dihydroxy-1,4benzenedicarboxaldehyde with Ni(OAc) ·4H2O. The Ni centers did not form nodes (as in metal covalent frameworks) but were immobilized on the side functional groups of the COF building blocks. The electrical conductivity of the Ni-COF thin film registered a value, of 1.2 S/cm. These remarkable electrical properties were attributed to the highly conjugated framework, wellstructured pores, and the presence of numerous redox centers. Consequently, the material exhibited an impressive specific capacitance of 1257 F g−1(in 3 m KOH, 1 A g−1, 3 electrode system) and it maintained 94% of its capacitance after 10 000 cycles. Moreover, when utilized in an asymmetric supercapacitor configuration (with activated carbon as the other electrode), the Ni-COF featured a high capacitance of 417 F g−1at a current density of 1 A g−1. Notably, it achieved an exceptional energy density of 130 Wh kg−1at a power density of 839 W kg−1, surpassing the performance of previously reported COF electrode materials. The electrochemical behavior of COF nanofibers was studied and compared with those of COF particles and hollow spheres by Dong et al. COF nanofibers exhibited higher overall pore volumes, more regular built-in vertically oriented channels, and larger BET-specific surface area compared to COF particles and hollow spheres.[334]With over 80% of the original capacitance retained after 10 000 cycles, the as-prepared COF nanofibers exhibited extraordinary cycling endurance with a maximum specific capacitance of up to 235 F g−1at 0.5 A g−1. These favorable performance features were also promoted by the 1D shape of the COF, boosting the charge transport. Zhang et al. synthesized iminebased COF by using the Schiff base reaction between TAPB and BPY (2,2′-bipyridyl-5,5′-dialdehyde).[335]The solvothermal and gas–liquid interface synthesis methods were used to create the bulk COF and self-supporting COF films, respectively. These bulk COF showed specific capacitance values of 633.4 F g−1at 1Ag −1and the thin-film COF 0.26 mF cm−2at 0.001 mA cm−2 for an ≈10 nm nanofilm. Moreover, COF nanofilms were modified by introducing Ni2+ions by the reversible redox reaction of Ni2+/Ni3+, where it was verified that Ni2+cations were coordinated on the N sites of the BPY molecules. The incorporation of single Ni2+cations resulted in the increase of the specific capacitance to 0.38 mF cm−2at 0.001 mA cm−2. In another report, using solvothermal Schiff base condensation between 1,3,5-triformylphloroglucinol (Tp) and 3,3’- diaminobenzidine, a new benzimidazole-based covalent organic polymer (TpDAB) was produced.[336]TpDAB showed outstanding rate capability, maintaining 93% of its original specific capacitance after 1000 cycles, and a specific capacitance of 335 F g−1at 2 mV s−1.The nitrogen functionalities of the TpDAB polymer with its microporosity were found to be responsible for the high electrochemical activity. A major advantage of some COF structures is their crystalline 2D architecture with highly unsaturated carbon-carbon bonds. Regarding this, a 2D conjugated COF with an olefin link (g-C34N6-COF) was recently reported.[337]An extended sp2bonded carbon skeleton with side cyanide ligands, a sheet structure, and crystalline layered architecture was formed using a variant of Knoevenagel condensation. The COF integrated 3,5dicyano-2,4,6-trimethylpyridine and 1,3,5-triazine units, resulting in improved 𝜋-electron communication and electrochemical activity. Its uniform nanofibrous morphology, when combined with carbon nanotubes, formed a flexible thin-film electrode. This electrode showed high performance in a microsupercapacitor, with an areal capacitance of 15.2 mF cm−2, high energy density (7.3 mWh cm−3), and remarkable rate capability. In another report, the first successful synthesis of a 2D COF with a fully sp2-bonded carbon skeleton was achieved, by using 2D poly(phenylenevinylene) (2DPPV). This COF was synthesized using a Knoevenagel polycondensation reaction involving 1,4phenylene diacetonitrile and three-armed aromatic aldehyde.[338] The subsequent annealing of the 2D PPV at high temperature delivered extremely porous nanosheets with a high SSA. These nanosheets exhibited enhanced electrochemical performance, especially in supercapacitor applications and ORR. As supercapacitor electrodes, they exhibited a capacitance of 0.5 A g−1in a 6 m KOH aqueous solution, and exceptional cycling stability with almost no capacitance loss even after 10 000 cycles. The energy density and power density of the 2DPPV material were 30 Wh kg−1and 6654 W kg−1, respectively. Also, a 2D PDC–MA– COF with redox-active triazine segments was produced using 1,4piperazinedicarboxaldehyde (PDC) and melamine (MA) as functional groups.[339]It exhibited large SSA (748.2 m2g−1), constricted pore thickness (1.9 nm), and a large pore volume (1.21 cm3g−1). The PDCMACOF delivered 335 F g−1of capacitance at the power density of 750 W kg−1with an energy density of 29.2 Wh kg−1. Using 2,5-dibromothiophene (DBT) and melamine (MA) organic linkers a new 2D COF structure (DBT-MA-COF) was synthesized with intralayer hydrogen bonding leading to a Adv. Energy Mater. 2024,14, 2400521 2400521 (37 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de flat and rigid structure.[340]The material’s quasi-reversible redox function, involving the reversible transformation of quinone in the triazine units, provided the basis for the generation of DBT-MA-COF pseudocapacitance. DBT-MA-COF had a significant heteroatom concentration in the triazine & thiophene moieties, which improved the transfer of electroactive species over the interface and promoted solution conductance. The assembled asymmetrical device with nitrogen-doped graphitized chitosan as the cathode material exhibited an energy density of 32.1 Wh kg−1 at the power density of 800 W kg−1with 83% capacitance retention after 30000 charging/discharging cycles. In general, pseudo capacitors require the assembly of porous electrode compositions containing extended conductive pathways, large surface coverage, and high ionic conductivity as a way to accelerate the further development of EES platforms. In this context, Phos-COF-1, a novel phosphine-based COF, was reported for SCs,[75]with a BET SSA of 818 m2g−1and a pore dimension of 1.56 nm and a microporous composition. The phosphine moieties in the Phos-COF-1 electrode demonstrated excellent reversible redox characteristics, resulting in a high energy density of 32 Wh kg−1. The electrochemical performance can also be improved by the existence of donor-acceptor conjugation and ion transport within the electrode material. For instance, the produced COF TPDA-1 with 1,3,5-tris(4-aminophenyl)triazine and 2,4,6-trihydroxyisophthalaldehyde linkers exhibited such a donor-acceptor conjugation responsible for the intense redox activity.[341]The TPDA-1 material delivered a significant capacitive performance of 469.4 F g−1at 2 mV s−1. Additionally, the material retained 95% of capacitance after 1000 cycles, validating the reversibility of redox reactions. Similarly, 1,3,5tris(4-aminophenyl) triazine with 2,6-diformyl-4-methylphenol was used to produce TDFP-1 COF. The material with 651 m2g−1 of SSA also demonstrated improved donor–acceptor features. The sample showed 354 F g−1of specific capacitance at 2 mV s−1. The presence of the conjugated polymeric scaffolding in the TDFP-1 COF facilitated the charge transport within the micropores. In another report, 1,3,5-triformylphloroglucinol (TFP) and 1,5-diaminonaphthalene were combined via solvothermal Schiff base condensation to form a porous and extended network in the TFP-NDA-COF (NDA) material.[342]When tested as a supercapacitor electrode, it delivered 379 F g−1of specific capacitance at the scan rate of 2 mV s−1with 75% capacitance retention after 8000 charging/discharging cycles. The permanent porosity and extended conjugated aromatic network were crucial for the fast ion and electron propagation within the electrode and the constant permeability of the framework boosted the electrocatalytic activity. The production of porous structures with variable diameter can further improve the ion transport capabilities of the materials. For instance, C3-symmetric benzotrithiophene tricarbaldehyde (BTT)-based COFs exhibited such an extended set of properties.[343]The rigid and planar conjugated structure of BTTs, the extended aromatic core due to the thiophene fused rings and the intermolecular 𝜋-stacking endows them with high charge transport properties. Moreover, the three-dimensional functionalization of BTTs with side groups is an effective strategy for improving their redox activity and system integration. The presence of conductive pathways in the electrode materials is a decisive factor that must be taken into consideration during the material’s engineering, because facilitates the fast electron transport from the electrodes to the current collectors and minimizes the device resistance. Therefore, growing COFs over conductive substrates is one of the simple but effective methods to produce efficient materials for supercapacitor applications. Han et al., for the first time, engineered nanocoatingscomposed of COFs grown onnickelnanowires(NiNWs), that gave significantly improved electrochemical performance for supercapacitors.[344]The electrode material constructed using COFs nanocoating delivered 314 F g−1of specific capacitance when discharged at 50 A g−1of current density. The presence of electrical and electrochemical features of NiNWs and the microporosity of COF were responsible for delivering high specific capacitance. Furthermore, Shanavaz et al. developed triazinebased COF via Schiff base formation using polycondensation reaction of melamine and terephthalaldehyde.[345]The COF was decorated with niobium cations to create a Nb@COF and studied as a supercapacitor electrode in a three-electrode setup. At a scan rate of 2 mV/s, Nb@COF showed enhanced specific capacitance (367 F g−1) in comparison to pure COF (244 F g−1). The porosity and interlayer spacing, as well as the pseudocapacitance in Nb@COF due to the Nb2+cations ascribed the system with better electrochemical performance. Even after 5000 cycles, Nb@COF demonstrated strong stability during charging– discharging, holding 89% of the initial specific capacitance. In another report, a novel benzimidazole-arylamide COF was synthesized through the condensation polymerization pathway exhibiting an SSA of 177 m2g−1and a pore diameter of 30–32 Å.[346]The sample showed fast ion transport and delivered 88.4 Fg −1of specific capacitance at 0.5 A g−1and 93.61% capacitance retention after 5000 discharging cycles in 1 m H3PO4electrolyte. SWCNTs coated with COFs were produced by in situ polymerization of TpPa-COF.[347]The supercapacitors tested based on this composite, combining the high conductivity of SWCNTs with the porosity and high redox potential of TpPa-high COF, delivered substantially higher capacitance than the pure COF, of 153 Fg −1at the current density of 0.5 A g−1. COFs may also improve their conductivity by introducing polymeric materials via postsynthesis modification. PANI-customized triazine-based COFs were recently prepared by Dutta et al. upon in situ polymerization of aniline inside the permeable COF scaffolds.[348]The sample showed high conductivity 1.4–1.9 ×10−2Scm −1at ambient temperature and a 20-fold improvement in specific capacitance over the pristine frameworks. The fabricated supercapacitor showed a high energy density of 24.4 Wh kg−1at the power density of 200 Wkg −1. Similarly, a 3D porphyrin-based COF supported on CNTs was synthesized by one-pot polymerization.[349]After annealing, the CNT N-doped carbon nanospheres (N-C@CNTs) were obtained that showed a specific capacitance of 250 F g−1. The distinctive architecture of these COF precursors, containing the flexible triangular pyramid-shaped tris(4-formylphenyl) amine and the rigid porphyrin units, allowed the creation of CNT twined Ndoped carbon nanocomposites, in addition to exposing active N entities onto the carbon surfaces. In another report, the electrical characteristics of COF thin layers were enhanced by in situ solidstate infiltration of carbon nanofibers (CNF) within the COF substrate.[350]The COF and CNF in the COF-CNF composites exhibited strong intermolecular interactions. Therefore, these COF-CNF blends (DqTp-CNF and DqDaTp-CNF) encoded high electrical conductance (103 S cm−1) and good electrochemical Adv. Energy Mater. 2024,14, 2400521 2400521 (38 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de Figure 19. Flexible Supercapacitor based on COF. a) SEM image of g-C34N6-COF (inset: optical photo of the electrode). b) SEM image of the COF layer. c) Schematic description of the method used for electrode preparation for g-C34N6-COF. d) GCD of g-C34N6-COF. Reproduced with permission.[337]Copyright Wiley, 2019. e) Schematic of COF/rGO aerogel, f) optical image of COF/rGO aerogel, g) SEM image of COF/rGO aerogel, h) Stress–strain behavior of COF/rGO aerogel, and i) cycling stability and (inset) cyclic charge–discharge performance of COF/rGO aerogel. Reproduced with permission.[185] Copyright 2020, Springer Nature. properties (464 mF cm−2at 0.25 mA cm−2). Further, integrating DqDaTp-CNF SC with a perovskite solar cell resulted into a unified self-charging power pack. After photo charging for 300 s, the developed self-charging power unit showed excellent device-level performance (42 mF cm−2). In another report, COF/rGO aerogels prepared by a hydrothermal method were successfully synthesized (Figure 19).[185]Upon freeze-drying, the COFs grown over the interface of the graphene layers, which were ordered in a 3D manner, culminated in a lightweight aerogel. The material featured a multilayer porous structure that could both compress and extend repeatedly without collapsing. In particular, the produced aerogel showed excellent stability against compression. When tested as a supercapacitor electrode, the aerogel delivered a high capacitance of 269 F g−1at 0.5 A g−1. The device retained almost 100% of its capacitance even after 5000 charging–discharging cycles. Furthermore, the COF/rGO composite was used to produce micro-supercapacitors which with 15.2 mF cm−2of aerial capacitance and 7.3 mWh cm−3of energy density. In an interesting report, Dong et al. developed COF crystallites by in situ growth along carbon skeleton surfaces, producing a carbon/rGOsupported COF composite foam utilizing a graphene-wrapped carbon foam.[351]When studied as self-supported electrodes for supercapacitors, the resultant composite foam provided a high capacitance of 129 F g−1at 0.5 A g−1. Moreover, after 20 000 cycles Adv. Energy Mater. 2024,14, 2400521 2400521 (39 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de at 10 A g−1, there was no discernible decrease in capacitance, suggesting outstanding long-cycling stability. Because the composite foam has a robust carbon backbone, it exhibits impressive compressibility and fatigue tolerance. This further permits the use of pre-fabricated composite foams that may be put together to create flexible supercapacitors. In another study, An et al. developed COF/MXenes thin films via cation-driven-self-assembly process for supercapacitor applications.[352]The superior intrinsic conductivity of MXenes and the ordered pore structure of COFs significantly boosted the electron transfer and ion migration rates. The integrated film electrode provided exceptional mechanical strength, good kinetic energy storage characteristics, and a capacitance of 390 F g−1at 0.5 A g−1with a capacitive contribution of 96.7% at 50 mV s−1. Supercapacitor electrodes benefit largely from using porous nanocarbons,graphene,andconductingpolymericmaterialsthat are rich in nitrogen.[353]However, for the electrode materials to be able to act efficiently requires high N doping concentration and large SSAs. For these reasons, the linkers with high N content can enrich the COF backbones and then, after pyrolysis, nanostructures can be obtained by combining the high concentration of N-center sites with the high porosity of the carbon structure. For instance, Suzuki coupling was used to create a porous aromatic framework (PAF) material (LNU-18) comprising two nitrogen atoms of different nature (N-triazine and Namine).[354]The porous aromatic framework, encompassing robust covalent bonds, expressed an N atom-rich chemical composition. The porous carbon structure with tailored nitrogen atoms (N-triazine and N-amine) improved the overall capacitance. The LNU-18 framework displayed a capacitance of 269 F g−1,which was 3–4 times better than the capacitance on a similar COF without N-doping. The role of N-doping was also verified in the case of a microporous N-doped carbon material which was produced by carbonizing ACOF1, which encoded an azine group connected to two structural lattices.[355]The produced microporous carbon exhibited 1596 m2g−1of surface area with 1 nm average pore size distribution. The micro-porous patterns were formed in the material as a result of the evolution of nitrogen gas during the thermal decomposition of the azine bond. Moreover, the N-doped centers were created in the structure in such a way that gave rise to redox activity. In another report, a covalent triazine-based framework (TCNQ-CTFs) was produced with a significant nitrogen concentration (>8%) and a very large SSA (>3600 m2g−1).[356]The material delivered an excellent power density (42.8 Wh kg−1), a high specific capacitance (380 F g−1), and excellent cycling reliability, with no capacity decrease after 10 000 cycles. In another report, an ultrafast microwave-driven method was used to produce polytriazine COF with extremely high N concentration (approximately 50.5 wt%) using melamine and cyanuric chloride as reactants.[357]The sample delivered 1256 Fg −1of specific capacitance at 1 mV/s and 656 F g−1at 1 A g−1. After 5000 cycles the sample retained 87.4% of its initial capacitance. Lavillunière et al. optimized the structure of COF-5 using a solvothermal technique aided by microwave radiation.[358]The practicality of microwave irradiation as an alternative method for COF synthesis was demonstrated, effectively synthesizing covalent organic framework-based compounds, including COFs with hexagonal structure. The obtained COFs displayed high crystallinity and electrical conductivity up to 2.35 ×10−2Scm −1.However the specific capacitance of the microwave-synthesized COF5 as an active electrode material in supercapacitor applications was mediocre, and even with conducting additives a specific capacitance of 85 F g−1at 2 mV s−1was achieved. It was found that only ≈15% of the active material was utilized in the electrochemical process, ascribed, probably, to poor ion transport at the interface between the COF-5 grains. This observation underscores the role of the continuous 1D structure of COF nanofibers, previously discussed, in improving the charge transport in the bulk of the electrode. Apart from the nitrogen content, other heteroatoms such as oxygen, sulfur, and boron also contribute to the redox activity and charge transfer properties. For instance, by using N and Orich triazine-driven PI (TPI-P/TPI-N) structures, N-doped porous carbon-based materials were synthesized through pyrolysis.[359] The material treated at 700 °C (TPI-P-700) gave a high specific capacity of 423 F g−1in 1 m H2SO4. Additionally, after 10 000 charge/discharge cycles, the material retained 100% of initial capacitance. In another report, a salt-assisted thermal decomposition procedure was used to decompose COFs structure. Using this strategy, O and N co-doped carbon (ONC-T1s) treated in presence of potassium carbonate (K2CO3) was successfully obtained.[360]The porous layered structure of ONC-T1s had a significant SSA (3451 m2g−1) and delivered an exceptional 1711 Fg −1of specific capacitance at 1 A g−1, and delivered an ultra-fast charge–discharge rate, with a specific capacitance of 856 F g−1at 500 A g−1. Besides O, COFs rich in N and boron (B) were also produced by reacting melamine and 4-formylphenylboronic acid in a single pot procedure to create B, N-codoped carbons (B-N-C).[361]In contrast to other microporous carbon plates obtained from COFs, the B-N-C material exhibited distinctive hollow capsule shapes and, notably, showed a dominant mesoporous nature. The formation of these hollow B-N-C capsules was attributed to the facile decomposition of melamine-boroxine organic building blocks and the templating role played by copper species such as Cu(NO3)2, Cu2(NO3)(OH)3, and Cu. The B-N-C capsules were very efficient in oxygen reduction reaction (ORR) in wide pH electrolytes, especially in alkaline solution. When tested in supercapacitors applications, the material acted as a sophisticated counter electrode with a capacitance of 230 F g−1. Upon mixing an activating agent with a COF during the pyrolysis step the SSA can be improved. In this context, a COF prepared from 2,5-dihydroxy1,4-benzoquinone and p-phenylenediamine was carbonized in the presence of KOH.[362]The derived DQPAC-700 displayed microporous characteristics with high SSA (16 607 m2g−1)and significant N/O concentrations (4.09 wt.% and 10.84 wt.%, respectively). In 6 m KOH solution, DQPAC-700 delivered the specific capacitance of 292 F g−1with 96% capacitance retention after 20 000 charging/discharging cycles. Activating agents can also be implanted in the material as functional units, specifically as halogen-based functionalities for the generation of novel electrodes. The halogen-functionalization approach has been reported to engineer rGO, carbon nanosheets, (CNS), CNTs, CTFs, and others.[363]Moreover, the electronic and geometric properties of pristine materials (including charge transfer, energy band gap, Gibbs free energy, electron spin density, localized electronic state, and topological defect) compared to those emerging from halogen inclusions are completely changed. Besides this, the Adv. Energy Mater. 2024,14, 2400521 2400521 (40 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de Table 3. Electrochemical performance comparison of different COF structures and its composites for supercapacitors. Materials Electrolyte Cs/CDEDPDCR/CNRefs. DAAQ-COF/GA 1 m H2SO4378/1 30.5 700 88.9/20000 [332] Ni-COF 3 m KOH 1257/1 130 839 94/10000 [333] TpDAB 1 m Na2SO4432/0.5 – – – [336] 2DPPV-800 6 m KOH 334/0.5 – – – [338] PDC-MA-COF 6 m KOH 335/1 29.2 750 88/200000 [339] DBT-MA-COF 6 m KOH 407/1 32.1 800 83/30000 [340] TPDA-1 1 m H2SO4348/0.5 – – – [341] TFP-NDA-COF 1 m H2SO4348/0.5 – – – [342] NiNWs@TpPaCOFs 1 m LiCl 426/2 – – – [344] BIBDZ 1 m H3PO488.4/0.5 – – – [346] DqDaTp-CNF 364mF cm−2/0.25 mA cm−25.8 μWh cm−2125 μWcm −276 (4500) [350] CMF 6 m KOH 390/0.5 27.5 350 88.9(20000) [352] LNU-18-800 6 m KOH 269/0.5 [354] TCNQ-CTF 1 m KOH 380/0.2 – – – [356] NENP-1 0.1 m H2SO4656/1 102 1600 – [357] TPI-P-700 1 m H2SO4423/1 10.5 – 100(6000) [359] ONC-T1-850 1 m H2SO41711/0.5 – – – [360] DQPAC-700 6 m KOH 292/0.5 11.3 103 96 (20000) [362] COF/rGO 0.5 m H2SO4269/0.5 – – – [185] SWCNTs-TpPa-COFs 1 m H2SO4153/0.5 – – – [347] PANI/TCOF-2 1 m H2SO4275/0.5 24.4 200 – [348] Abbreviations: ED-Energy Density (Wh kg−1), PD-Power Density (W kg−1), CsSpecific Capacitance (F g−1), CD-current density (A g−1), CR-Capacitance Retention (%), CN-Cycle Number Note: ED, PD and CRare reported for 2-electrode setup for supercapacitor device. introduction of functional groups and metals through doping further equips COFs to function as pseudocapacitive materials. The availability of a wide range of linkers, can introduce to the COF nand p-type functionalities, which can serve two purposes at the same time. Very recently, Gu et al. produced COF with n-type imide and p-type quaternary nitrogen centers to support the adsorption of Li+as well as PF6−.[364]The material showed 91% capacity retention after 4000 cycles with 165 mAh g−1of capacity at 30 mA g−1of discharge rate. From all these studies, it is evident that the field of COFs is emerging rapidly for supercapacitor applications. However, the research on supercapacitors is explored majorly on the laboratory scale, and before it is applied on an industrial scale, a number of obstacles pertaining to cost and availability of materials must be resolved. Table 3presents the performance characteristics of different COFs and COFs composite materials as electrodes for supercapacitors. 8. Critical Assessment of Application of COFs in Batteries and Supercapacitors Considerable efforts are dedicated to the discovery of innovative materials and chemical compositions that can enhance energy storage performance. Among the various materials being explored, COFs have been employed in the research for both supercapacitors and batteries.[319,365–369]The structural customizability of COFs, achieved through the use of different linker combinations, enables the creation of diverse pore networks and size distributions, functional groups, reactivity profiles, and stabilities in these EES devices. The field of COF materials has not yet witnessed an explosive growth, but over the past decade, there have been substantial advances and interest in synthetic methods and COF designs. In terms of COFs’ ability to address various challenges in the realm of energy storage, they stand as emerging candidates with other innovative materials like MOFs and MXenes. However, despite a decade of research, the COF field in energy storage cannot be considered mature enough for commercialization. Numerous critical issues and challenges must be addressed before their practical application becomes feasible. The primary prerequisites for a material that will be used in an energy storage device are the conductivity and redox activity. One of the main problems preventing COFs from performing at a high electrochemical level is the witnessed low redox activity and electrical conductivity. To increase the overall activity and conductivity, post-modification techniques can be used to overcome this issue, such as addition of metal ions or conductive agents. Among different conductive agents, conducting polymers have been frequently employed in the past few decades to increase the conductivity and redox activity of different materials.[370]By combining COF with compounds like PEDOT, PPy, polyaniline, the conductive channels and electrochemical activity can be enhanced.[371,372]Electrochemical techniques can be used to infiltrate conducting polymers inside the COF structure.[373]The strong redox activity of the conducting polymers is an advantage over the use of activated carbons, CNTs, or graphene. While the conducting polymers may provide efficient conductive pathways Adv. Energy Mater. 2024,14, 2400521 2400521 (41 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de [225] K. (Kelvin) Fu, Y. Gong, G. T. Hitz, D. W. McOwen, Y. Li, S. Xu, Y. Wen, L. Zhang, C. Wang, G. Pastel, J. Dai, B. Liu, H. Xie, Y. Yao, E. D. Wachsman, L. Hu, Energy Environ. Sci. 2017,10, 1568. [226] Y. Kato, S. Hori, T. Saito, K. Suzuki, M. Hirayama, A. Mitsui, M. Yonemura, H. Iba, R. Kanno, Nat. Energy 2016,1, 16030. [227] H. Chen, H. Tu, C. Hu, Y. Liu, D. Dong, Y. Sun, Y. Dai, S. Wang, H. Qian, Z. Lin, L. Chen, J. Am. Chem. Soc. 2018,140, 896. [228] Y. Zhang, J. Duan, D. Ma, P. Li, S. Li, H. Li, J. Zhou, X. Ma, X. Feng, B. Wang, Angew. Chem., Int. Ed. 2017,56, 16313. [229] S. S. Park, Y. Tulchinsky, M. Dinc˘ a, J. Am. Chem. Soc. 2017,139, 13260. [230] Z. Wang, R. Tan, H. Wang, L. Yang, J. Hu, H. Chen, F. Pan, Adv. Mater. 2018,30, 1704436. [231] P. Knauth, Solid State Ion. 2009,180, 911. [232] H. Adenusi, G. A. Chass, S. Passerini, K. V. Tian, G. Chen, Adv. Energy Mater. 2023,13, 2203307. [233] H. Wu, H. Jia, C. Wang, J.-G. Zhang, W. Xu, Adv. Energy Mater. 2021, 11, 2003092. [234] K. Jeong, S. Park, G. Y. Jung, S. H. Kim, Y.-H. Lee, S. K. Kwak, S.-Y. Lee, J. Am. Chem. Soc. 2019,141, 5880. [235] Y. Zheng, S. Xia, F. Dong, H. Sun, Y. Pang, J. Yang, Y. Huang, S. Zheng, Adv. Funct. Mater. 2021,31, 2006159. [236] X. Li, K. P. Loh, ACS Mater. Lett. 2019,1, 327. [237] X. Liang, Y. Tian, Y. Yuan, Y. Kim, Adv. Mater. 2021,33, 2105647. [238] Z. Gadjourova, Y. G. Andreev, D. P. Tunstall, P. G. Bruce, Nature 2001,412, 520. [239] X. Li, Q. Hou, W. Huang, H.-S. Xu, X. Wang, W. Yu, R. Li, K. Zhang, L. Wang, Z. Chen, K. Xie, K. P. Loh, ACS Energy Lett. 2020,5, 3498. [240] M. D. Tikekar, S. Choudhury, Z. Tu, L. A. Archer, Nat. Energy 2016, 1, 16114. [241] X. Yang, Y. Hu, N. Dunlap, X. Wang, S. Huang, Z. Su, S. Sharma, Y. Jin, F. Huang, X. Wang, S. Lee, W. Zhang, Angew. Chem., Int. Ed. 2020,59, 20385. [242] L. Bai, Q. Gao, Y. Zhao, J. Mater. Chem. A 2016,4, 14106. [243] S. Feng, H. Xu, C. Zhang, Y. Chen, J. Zeng, D. Jiang, J.-X. Jiang, Chem. Commun. 2017,53, 11334. [244] G. Zhao, Y. Zhang, Z. Gao, H. Li, S. Liu, S. Cai, X. Yang, H. Guo, X. Sun, ACS Energy Lett. 2020,5, 1022. [245] X. Yu, C. Li, Y. Ma, D. Li, H. Li, X. Guan, Y. Yan, V. Valtchev, S. Qiu, Q. Fang, Microporous Mesoporous Mater. 2020,299, 110105. [246] E. R. Wolfson, N. Xiao, L. Schkeryantz, W. Karl Haug, Y. Wu, P. L. McGrier, Mol Syst Des Eng 2020,5, 97. [247] S. Haldar, K. Roy, S. Nandi, D. Chakraborty, D. Puthusseri, Y. Gawli, S. Ogale, R. Vaidhyanathan, Adv. Energy Mater. 2018,8, 1702170. [248] O. Buyukcakir, J. Ryu, S. H. Joo, J. Kang, R. Yuksel, J. Lee, Y. Jiang, S. Choi, S. H. Lee, S. K. Kwak, S. Park, R. S. Ruoff, Adv. Funct. Mater. 2020,30, 2003761. [249] T. Zhou, Y. Zhao, J. W. Choi, A. Coskun, Angew. Chem. 2019,131, 16951. [250] S. Haldar, K. Roy, R. Kushwaha, S. Ogale, R. Vaidhyanathan, Adv. Energy Mater. 2019,9, 1902428. [251] G. Zhuang, Y. Gao, X. Zhou, X. Tao, J. Luo, Y. Gao, Y. Yan, P. Gao, X. Zhong, J. Wang, Chem. Eng. J. 2017,330, 1255. [252] Y.-J. Lei, H.-W. Liu, Z. Yang, L.-F. Zhao, W.-H. Lai, M. Chen, H. Liu, S. Dou, Y.-X. Wang, Adv. Funct. Mater. 2023,33, 2212600. [253] E. Goikolea, V. Palomares, S. Wang, I. R. de Larramendi, X. Guo, G. Wang, T. Rojo, Adv. Energy Mater. 2020,10, 2002055. [254] R. Rajagopalan, Y. Tang, X. Ji, C. Jia, H. Wang, Adv. Funct. Mater. 2020,30, 1909486. [255] J. Hu, Y. Hong, M. Guo, Y. Hu, W. Tang, S. Xu, S. Jia, B. Wei, S. Liu, C. Fan, Q. Zhang, Energy Storage Mater. 2023,56, 267. [256] M.-S. Kim, W.-J. Lee, S.-M. Paek, J. K. Park, ACS Appl. Mater. Interfaces 2018,10, 32102. [257] J. Liu, P. Lyu, Y. Zhang, P. Nachtigall, Y. Xu, Adv. Mater. 2018,30, 1705401. [258] B. Chandra Patra, S. Kanti Das, A. Ghosh, A. Raj K, P. Moitra, M. Addicoat, S. Mitra, A. Bhaumik, S. Bhattacharya, A. Pradhan, J. Mater. Chem. A 2018,6, 16655. [259] R. van der Jagt, A. Vasileiadis, H. Veldhuizen, P. Shao, X. Feng, S. Ganapathy, N. C. Habisreutinger, M. A. van der Veen, C. Wang, M. Wagemaker, S. van der Zwaag, A. Nagai, Chem. Mater. 2021,33, 818. [260] M.-M. Hu, H. Huang, Q. Gao, Y. Tang, Y. Luo, Y. Deng, L. Zhang, Energy Fuels 2021,35, 1851. [261] H. Ha, S. Nam, S.-H. Jeong, S. Hyun, J. Mech. Sci. Technol. 2019,33, 3865. [262] R. Shi, L. Liu, Y. Lu, C. Wang, Y. Li, L. Li, Z. Yan, J. Chen, Nat. Commun. 2020,11, 178. [263] L. Zhang, R. Wang, Z. Liu, J. Wan, S. Zhang, S. Wang, K. Hua, X. Liu, X. Zhou, X. Luo, X. Zhang, M. Cao, H. Kang, C. Zhang, Z. Guo, Adv. Mater. 2023,35, 2210082. [264] S. Gu, S. Wu, L. Cao, M. Li, N. Qin, J. Zhu, Z. Wang, Y. Li, Z. Li, J. Chen, Z. Lu, J. Am. Chem. Soc. 2019,141, 9623. [265] Y. Zhang, Z. Gao, Electrochim. Acta 2019,301, 23. [266] J. Lee, H. Lim, J. Park, M.-S. Kim, J.-W. Jung, J. Kim, I.-D. Kim, Adv. Energy Mater. 2023,13, 2300442. [267] Q. Xu, Q. Li, Y. Guo, D. Luo, J. Qian, X. Li, Y. Wang, Small Methods 2020,4, 2000159. [268] X. Chen, H. Zhang, C. Ci, W. Sun, Y. Wang, ACS Nano 2019,13, 3600. [269] Y. Qiu, W. Li, W. Zhao, G. Li, Y. Hou, M. Liu, L. Zhou, F. Ye, H. Li, Z. Wei, S. Yang, W. Duan, Y. Ye, J. Guo, Y. Zhang, Nano Lett. 2014,14, 4821. [270] S. Feng, Z.-H. Fu, X. Chen, Q. Zhang, InfoMat 2022,4, 12304. [271] L. Yang, W. Wei, Y. Ma, Y. Xu, G. Chang, J. Power Sources 2020,449, 227551. [272] Y. Zu, Y. Xu, L. Ma, Q. Kang, H. Yao, J. Hou, ACS Appl. Mater. Interfaces 2020,12, 18457. [273] P. Jia, T. Hu, Q. He, X. Cao, J. Ma, J. Fan, Q. Chen, Y. Ding, J. Pyun, J. Geng, ACS Appl. Mater. Interfaces 2019,11, 3087. [274] B.-Y. Lu, Z.-Q. Wang, F.-Z. Cui, J.-Y. Li, X.-H. Han, Q.-Y. Qi, D.-L. Ma, G.-F. Jiang, X.-X. Zeng, X. Zhao, ACS Appl. Mater. Interfaces 2020,12, 34990. [275] R. Guan, L. Zhong, S. Wang, D. Han, M. Xiao, L. Sun, Y. Meng, ACS Appl. Mater. Interfaces 2020,12, 8296. [276] N. Deng, Y. Liu, W. Yu, J. Kang, Q. Li, H. Gao, L. Zhang, W. Kang, Y. Liu, B. Cheng, Energy Storage Mater. 2022,46, 29. [277] X. Song, F. Zhou, M. Yao, C. Hao, J. Qiu, ACS Sustainable Chem. Eng. 2020,8, 10185. [278] H. Shin, D. Kim, H. J. Kim, J. Kim, K. Char, C. T. Yavuz, J. W. Choi, Chem. Mater. 2019,31, 7910. [279] T. Zhang, F. Hu, C. Song, S. Li, W. Shao, S. Liu, H. Peng, S. Hu, X. Jian, Chem. Eng. J. 2021,407, 127141. [280] S. Royuela, J. Almarza, M. J. Mancheño, J. C. Pérez-Flores, E. G. Michel, M. M. Ramos, F. Zamora, P. Ocón, J. L. Segura, Chemistry 2019,25, 12394. [281] Z. Li, H.-Y. Zhou, F.-L. Zhao, T.-X. Wang, X. Ding, B.-H. Han, W. Feng, Chin.J.Polym.Sci.2020,38, 550. [282] X.-F. Liu, H. Chen, R. Wang, S.-Q. Zang, T. C. W. Mak, Small 2020, 16, 2002932. [283] Y. Ge, J. Li, Y. Meng, D. Xiao, Nano Energy 2023, 108297. [284] H. Liao, H. Ding, B. Li, X. Ai, C. Wang, J. Mater. Chem. A 2014,2, 8854. [285] H. Liao, H. Wang, H. Ding, X. Meng, H. Xu, B. Wang, X. Ai, C. Wang, J. Mater. Chem. A 2016,4, 7416. [286] Y. Meng, G. Lin, H. Ding, H. Liao, C. Wang, J. Mater. Chem. A 2018, 6, 17186. Adv. Energy Mater. 2024,14, 2400521 2400521 (48 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de [287] D.-G. Wang, N. Li, Y. Hu, S. Wan, M. Song, G. Yu, Y. Jin, W. Wei, K. Han, G.-C. Kuang, W. Zhang, ACS Appl. Mater. Interfaces 2018,10, 42233. [288] J. Kim, A. Elabd, S.-Y. Chung, A. Coskun, J. W. Choi, Chem. Mater. 2020,32, 4185. [289] X. Chen, Y. Xu, F.-H. Du, Y. Wang, Small Methods 2019,3, 1900338. [290] J. Wang, L. Si, Q. Wei, X. Hong, L. Lin, X. Li, J. Chen, P. Wen, Y. Cai, JEnergyChem2019,28, 54. [291] R. Meng, Q. Deng, C. Peng, B. Chen, K. Liao, L. Li, Z. Yang, D. Yang, L. Zheng, C. Zhang, J. Yang, Nano Today 2020,35, 100991. [292] A. Khayum M, M. Ghosh, V. Vijayakumar, A. Halder, M. Nurhuda, S. Kumar, M. Addicoat, S. Kurungot, R. Banerjee, Chem. Sci. 2019, 10, 8889. [293] D. Ma, H. Zhao, F. Cao, H. Zhao, J. Li, L. Wang, K. Liu, Chem. Sci. 2022,13, 2385. [294] H. Li, M. Cao, Z. Fu, Q. Ma, L. Zhang, R. Wang, F. Liang, T. Zhou, C. Zhang, Chem. Sci. 2024. [295] M. Yu, N. Chandrasekhar, R. K. M. Raghupathy, K. H. Ly, H. Zhang, E. Dmitrieva, C. Liang, X. Lu, T. D. Kühne, H. Mirhosseini, I. M. Weidinger, X. Feng, J. Am. Chem. Soc. 2020,142, 19570. [296] Y. Du, X. Gao, S. Li, L. Wang, B. Wang, Chin. Chem. Lett. 2020,31, 609. [297] B. Lu, W. Li, D. Cheng, B. Bhamwala, M. Ceja, W. Bao, C. Fang, Y. S. Meng, Adv. Energy Mater. 2022,12, 2202012. [298] Y. Zhao, K. Feng, Y. Yu, Adv. Sci. 2024,11. [299] G. Li, Z. Zhao, S. Zhang, L. Sun, M. Li, J. A. Yuwono, J. Mao, J. Hao, J. (Pimm) Vongsvivut, L. Xing, C.-X. Zhao, Z. Guo, Nat. Commun. 2023,14, 6526. [300] Z. Liu, G. Li, M. Xi, Y. Huang, H. Li, H. Jin, J. Ding, S. Zhang, C. Zhang, Z. Guo, Angew. Chem. n/a, 202319091. [301] C. Li, R. Kingsbury, L. Zhou, A. Shyamsunder, K. A. Persson, L. F. Nazar, ACS Energy Lett. 2022,7, 533. [302] Y. Zhang, M. Zhu, G. Wang, F.-H. Du, F. Yu, K. Wu, M. Wu, S.-X. Dou, H.-K. Liu, C. Wu, Small Methods 2021,5, 2100650. [303] J. Wang, Y. Yang, Y. Zhang, Y. Li, R. Sun, Z. Wang, H. Wang, Energy Storage Mater. 2021,35, 19. [304] J. H. Park, M.-J. Kwak, C. Hwang, K.-N. Kang, N. Liu, J.-H. Jang, B. A. Grzybowski, Adv. Mater. 2021,33, 2101726. [305] G. Li, X. Wang, S. Lv, J. Wang, X. Dong, D. Liu, Chem. Eng. J. 2022, 450, 138116. [306] C. Guo, J. Zhou, Y. Chen, H. Zhuang, Q. Li, J. Li, X. Tian, Y. Zhang, X. Yao, Y. Chen, S.-L. Li, Y.-Q. Lan, Angew. Chem. 2022,134, 202210871. [307] Q. Cao, L. Wan, Z. Xu, W. Kuang, H. Liu, X. Zhang, W. Zhang, Y. Lu, Y. Yao, B. Wang, K. Liu, Adv. Mater. n/a, 2210550. [308] B.-Q. Li, S.-Y. Zhang, B. Wang, Z.-J. Xia, C. Tang, Q. Zhang, Energy Environ. Sci. 2018,11, 1723. [309] Y. Zhang, C. Wei, M.-X. Wu, Y. Wang, H. Jiang, G. Zhou, X. Tang, X. Liu, Chem. Eng. J. 2023,451, 138915. [310] R. Sun, S. Hou, C. Luo, X. Ji, L. Wang, L. Mai, C. Wang, Nano Lett. 2020,20, 3880. [311] S. Zhang, Y.-L. Zhu, S. Ren, C. Li, X.-B. Chen, Z. Li, Y. Han, Z. Shi, S. Feng, J. Am. Chem. Soc. 2023,145, 17309. [312] H. Lu, F. Ning, R. Jin, C. Teng, Y. Wang, K. Xi, D. Zhou, G. Xue, ChemSusChem 2020,13, 3447. [313] Y. Liu, Y. Lu, A. Hossain Khan, G. Wang, Y. Wang, A. Morag, Z. Wang, G. Chen, S. Huang, N. Chandrasekhar, D. Sabaghi, D. Li, P. Zhang, D. Ma, E. Brunner, M. Yu, X. Feng, Angew. Chem., Int. Ed. 2023,62, 202306091. [314] Q. Xu, K. Zhang, J. Qian, Y. Guo, X. Song, H. Pan, D. Wang, X. Li, ACS Appl. Energy Mater. 2019,2, 5793. [315] J. Wang, W. Qin, X. Zhu, Y. Teng, Energy 2020,199, 117372. [316] P. Li, H. Lv, Z. Li, X. Meng, Z. Lin, R. Wang, X. Li, Adv. Mater. 2021, 33, 2007803. [317] Y. Wen, X. Wang, Y. Yang, M. Liu, W. Tu, M. Xu, G. Sun, S. Kawaguchi, G. Cao, W. Li, J. Mater. Chem. A 2019,7, 26540. [318] W. Sun, J. Zhang, M. Xie, D. Lu, Z. Zhao, Y. Li, Z. Cheng, S. Zhang, H. Chen, Nano Lett. 2020,20, 8120. [319] K. Zhang, X. Li, L. Ma, F. Chen, Z. Chen, Y. Yuan, Y. Zhao, J. Yang, J. Liu, K. Xie, K. P. Loh, ACS Nano 2023,17, 2901. [320] H. Wang, J. Jiang, T. Wan, Y. Luo, G. Liu, J. Li, J. Colloid Interface Sci. 2023,638, 542. [321] C. Zhan, T. Wu, J. Lu, K. Amine, Energy Environ. Sci. 2018,11, 243. [322] Y. Xu, Y. Zhou, T. Li, S. Jiang, X. Qian, Q. Yue, Y. Kang, Energy Storage Mater. 2020,25, 334. [323] S. Bian, G. Huang, Y. Xuan, B. He, J. Liu, B. Xu, G. Zhang, J. Membr. Sci. 2023,669, 121268. [324] V. Shrivastav, S. Sundriyal, A. Kaur, U. K. Tiwari, S. Mishra, A. Deep, J. Alloys Compd. 2020,843, 155992. [325] V. Shrivastav, S. Sundriyal, P. Goel, V. Shrivastav, U. K. Tiwari, A. Deep, Electrochim. Acta 2020,345, 136194. [326] S. Sundriyal, V. Shrivastav, A. Kaur, P. Dubey, S. Mishra, A. Deep, S. R. Dhakate, IEEE Trans. Nanotechnol. 2021,20, 481. [327] S. Sundriyal, V. Shrivastav, S. Mishra, A. Deep, Int. J. Hydrog. Energy 2020,45, 30859. [328] S.-Y. Lu, M. Jin, Y. Zhang, Y.-B. Niu, J.-C. Gao, C. M. Li, Adv. Energy Mater. 2018,8, 1702545. [329] S. Sundriyal, V. Shrivastav, A. Gupta, V. Shrivastav, A. Deep, S. R. Dhakate, Mater. Res. Bull. 2021,142, 111396. [330] S. Sundriyal, V. Shrivastav, S. K. Bhardwaj, S. Mishra, A. Deep, Electrochim. Acta 2021,380, 138229. [331] T. Li, X. Yan, Y. Liu, W.-D. Zhang, Q.-T. Fu, H. Zhu, Z. Li, Z.-G. Gu, Polym. Chem. 2020,11, 47. [332] N. An, Z. Guo, J. Xin, Y. He, K. Xie, D. Sun, X. Dong, Z. Hu, J. Mater. Chem. A 2021,9, 16824. [333] T. Li, W.-D. Zhang, Y. Liu, Y. Li, C. Cheng, H. Zhu, X. Yan, Z. Li, Z.-G. Gu, J. Mater. Chem. A 2019,7, 19676. [334] Y. Dong, X. Zhang, Y. Wang, L. Tang, Y. Yang, J. Power Sources 2023, 564, 232873. [335] J. Zhang, Z. Zhang, X. Xing, X. Xu, X. Zhang, H. Liu, P. He, P. Ren, B. Zhang, Dalton Trans. 2023,53, 223. [336] B. C. Patra, S. Khilari, L. Satyanarayana, D. Pradhan, A. Bhaumik, Chem. Commun. 2016,52, 7592. [337] J. Xu, Y. He, S. Bi, M. Wang, P. Yang, D. Wu, J. Wang, F. Zhang, Angew. Chem. 2019,131, 12193. [338] X. Zhuang, W. Zhao, F. Zhang, Y. Cao, F. Liu, S. Bi, X. Feng, Polym. Chem. 2016,7, 4176. [339] L. Li, F. Lu, R. Xue, B. Ma, Q. Li, N. Wu, H. Liu, W. Yao, H. Guo, W. Yang, ACS Appl. Mater. Interfaces 2019,11, 26355. [340] L. Li, F. Lu, H. Guo, W. Yang, Microporous Mesoporous Mater. 2021, 312, 110766. [341] P. Bhanja, S. K. Das, K. Bhunia, D. Pradhan, T. Hayashi, Y. Hijikata, S. Irle, A. Bhaumik, ACS Sustainable Chem. Eng. 2018,6, 202. [342] S. K. Das, K. Bhunia, A. Mallick, A. Pradhan, D. Pradhan, A. Bhaumik, Microporous Mesoporous Mater. 2018,266, 109. [343] S. Santi, S. Rossi, Tetrahedron Lett. 2019,60, 151021. [344] Y. Han, N. Hu, S. Liu, Z. Hou, J. Liu, X. Hua, Z. Yang, L. Wei, L. Wang, H. Wei, Nanotechnology 2017,28, 33LT01. [345] H. Shanavaz, B. P. Prasanna, S. Archana, M. K. Prashanth, F. A. Alharthi, R. Zhou, M. S. Raghu, B.-H. Jeon, K. Y. Kumar, J. Energy Storage 2023,67, 107561. [346] A. Roy, S. Mondal, A. Halder, A. Banerjee, D. Ghoshal, A. Paul, S. Malik, Eur. Polym. J. 2017,93, 448. [347] Y. Han, Q. Zhang, N. Hu, X. Zhang, Y. Mai, J. Liu, X. Hua, H. Wei, Chin. Chem. Lett. 2017,28, 2269. [348] T. K. Dutta, A. Patra, Chem Asian J 2021,16, 158. [349] R. Li, L. Xing, A. Chen, X. Zhang, A. Kong, Y. Shan, Ionics 2020,26, 927. Adv. Energy Mater. 2024,14, 2400521 2400521 (49 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de [350] A. K. Mohammed, V. Vijayakumar, A. Halder, M. Ghosh, M. Addicoat, U. Bansode, S. Kurungot, R. Banerjee, ACS Appl. Mater. Interfaces 2019,11, 30828. [351] Y. Dong, Y. Wang, X. Zhang, Q. Lai, Y. Yang, Chem. Eng. J. 2022,449, 137858. [352] N. An, Z. Guo, C. Guo, M. Wei, D. Sun, Y. He, W. Li, L. Zhou, Z. Hu, X. Dong, Chem. Eng. J. 2023,458, 141434. [353] M. Yang, Z. Zhou, Adv. Sci. 2017,4, 1600408. [354] Y. Zhao, N. Bu, H. Shao, Q. Zhang, B. Feng, Y. Xu, G. Zheng, Y. Yuan, Z. Yan, L. Xia, New J. Chem. 2019,43, 18158. [355] G. Kim, J. Yang, N. Nakashima, T. Shiraki, Chemistry 2017,23, 17504. [356] Y. Li, S. Zheng, X. Liu, P. Li, L. Sun, R. Yang, S. Wang, Z.-S. Wu, X. Bao, W.-Q. Deng, Angew. Chem. 2018,130, 8124. [357] M. Chaudhary, A. K. Nayak, R. Muhammad, D. Pradhan, P. Mohanty, ACS Sustainable Chem. Eng. 2018,6, 5895. [358] H. Lavillunière, T.-N. Pham-Truong, T.-K.-L. Nguyen, C. Vancaeyzeele, P.-H. Aubert, ACS Appl. Energy Mater. 2024. [359] N. Deka, R. Patidar, S. Kasthuri, N. Venkatramaiah, G. K. Dutta, Mater. Chem. Front. 2019,3, 680. [360] D. Yan, Y. Wu, R. Kitaura, K. Awaga, J. Mater. Chem. A 2019,7, 26829. [361] Z. Zhou, X. Zhang, L. Xing, J. Liu, A. Kong, Y. Shan, Electrochim. Acta 2019,298, 210. [362] B. Tang, L. Zheng, X. Dai, H. Chen, J. Energy Storage 2019,26, 100961. [363] W. Ye, H. Wang, J. Shen, S. Khan, Y. Zhong, J. Ning, Y. Hu, Chin. Chem. Lett. 2023,34, 107198. [364] S. Gu, J. Chen, R. Hao, X. Chen, Z. Wang, I. Hussain, G. Liu, K. Liu, Q. Gan, Z. Li, H. Guo, Y. Li, H. Huang, K. Liao, K. Zhang, Z. Lu, Chem. Eng. J. 2023,454, 139877. [365] A. Chatterjee, J. Sun, K. S. Rawat, V. Van Speybroeck, P. Van Der Voort, Small n/a, 2303189. [366] L. Liu, D. Cui, S. Zhang, W. Xie, C. Yao, N. Xu, Y. Xu, Dalton Trans. 2023,52, 6138. [367] B. Hu, J. Xu, Z. Fan, C. Xu, S. Han, J. Zhang, L. Ma, B. Ding, Z. Zhuang, Q. Kang, X. Zhang, Adv. Energy Mater. 2023,13, 2203540. [368] Y. Wang, M. Li, T. Wen, G. Gu, Nanotechnology 2023,34, 375402. [369] Y. Lin, H. Cui, C. Liu, R. Li, S. Wang, G. Qu, Z. Wei, Y. Yang, Y. Wang, Z. Tang, H. Li, H. Zhang, C. Zhi, H. Lv, Angew. Chem. 2023,135, 202218745. [370] S. K. Pati, D. Patra, S. Muduli, S. Mishra, S. Park, Small 2023,19, 2300689. [371] N. Sahiner, S. Demirci, J. Porous Mater. 2019,26, 481. [372] S. Haldar, D. Rase, P. Shekhar, C. Jain, C. P. Vinod, E. Zhang, L. Shupletsov, S. Kaskel, R. Vaidhyanathan, Adv. Energy Mater. 2022, 12, 2200754. [373] N. M. Yousif, O. M. Gomaa, Environ. Technol. 2023,0,1. [374] I. Hussain, M. Z. Ansari, C. Lamiel, T. Hussain, M. S. Javed, T. Kaewmaraya, M. Ahmad, N. Qin, K. Zhang, ACS Energy Lett. 2023, 8, 1887. [375] E. Tylianakis, E. Klontzas, G. E. Froudakis, Nanoscale 2011,3, 856. [376] N. Yang, S. Yu, W. Zhang, H.-M. Cheng, P. Simon, X. Jiang, Adv. Mater. 2022,34, 2202380. [377] X. Song, X. Xu, J. Liu, ChemNanoMat 2023,9, 202300246. Prashant Dubey recentlycompleted hisPh.D.inchemicalsciencesfromtheAcademyofScientificand InnovativeResearch (AcSIR-NPL),New Delhi,IndiainMarch2024.Hisresearchinterestsinclude thesynthesisofdifferentbio-waste-derivedactivatedcarbon,conductingpolymers,metal–organic frameworks,and theircompositesforsupercapacitors.Also,hehasagoodhandinthepreparation offree-standing carbon-basedelectrodesforsupercapacitorapplications.Hehaspublishedmore than20 articlesinreputedinternationaljournals.HeisthewinneroftheprestigiousRaman-Charpak visitingfellowship ofFrance, andrecentlyreceivedanEarlyCareerPostdoctoralFellowshipfromthe IndianInstitute ofTechnologyGandhinagar,India. Vishal Shrivastav ispresentlyworkingasanassistantprofessorattheInstituteofPhysicalChemistry, Poland.He hascompletedhisPh.D.(physicalsciences)intheareaofhybridelectrochemicalcapacitorsfromtheAcademyofScientificandInnovativeResearch(AcSIR-CSIO),Chandigarh,India.His researchinterests arethesynthesisandcharacterizationofMetalOrganicFrameworks derivedfrom nanoporouscarbon andmetaloxidesandfurthertheircompositeswithtransitionmetaldichalcogenidesfor hybridelectrochemicalcapacitorapplications.Hehaspublished24articlesinreputed internationaljournals.HeisthewinneroftheMarie-CuriecofoundedPASIFICfellowshipofPoland andTÜB˙ ITAKfellowshipofTurkey. Adv. Energy Mater. 2024,14, 2400521 2400521 (50 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de Tribani Boruah iscurrentlyaPh.D.candidate(SchoolofChemistry,CardiffUniversity,UnitedKingdom).After obtaininghermaster’s(DelhiUniversity),shejoinedtheNationalPhysicalLaboratory, India,wheresheworkedonthesynthesisofnano-fibersthroughelectrospinning.Thensheworkedat theInstitute ofNano-ScienceandTechnology,India,whereshefocusedonsingle-atomcatalystsfor energyconversion.In2023,shejoinedanindustrialPhDprogram(CardiffUniversity)fundedbyTOK JapanCompany,focusingonthesynthesisoftransitionmetalcomplexesforsemiconductorapplicationsanddensityfunctionaltheory.Additionally,sheisworkingontheflowelectrochemicalorganic transformationusing microfluidics. Giorgio Zoppellaro holdspositionsofseniorresearcheratRCPTMoftheCzechAdvancedTechnology andResearch Institute(CATRIN,PalackyUniversityOlomouc,CzechRepublic) andat VSB-Technical UniversityofOstrava.HeobtainedhisPh.D.degreeinchemistryatTheJohannesGutenbergUniversitätin Mainz(Germany;2004)andhabilitationtoassociateprofessorofChemistryinItaly(2017).His researchfocuses ontheapplicationoftheelectronparamagneticresonancetechniqueattheinterface ofmaterial science/photophysics/biomedicine. Radek Zboˇ ril actsastheScientificDirectoroftheRCPTMdivisionoftheCzechAdvancedTechnology andResearch Institute(CATRIN)atPalackyUniversityinOlomouc anda headoftheMaterials-Envi Labat VSB-TechnicalUniversityOstravaintheCzechRepublic.Heisanexpertinnanotechnologiesandtheauthorofover650papersinprestigiousjournalsincludingNatureNanotechnology (4x)or NatureCatalysis.Hispublications havereceived over68000citationsandhisH-indexis117 (GoogleScholar, April2024).ProfessorZboˇ rilhasappearedseveraltimesonthelistofHighlyCited Researchersannounced byClarivateAnalytics. Aristides Bakandritsos isthe headof aresearchdivisioninRCPTMoftheCzechAdvancedTechnology andResearch Institute(CATRIN,PalackyUniversityOlomouc,CzechRepublic) andsenior researcher atVSB-TechnicalUniversityofOstrava.HereceivedhisPhDinGreeceandhewasafacultymemberat theDepartmentofMaterialsScience,UniversityofPatras,beforejoiningCATRIN-RCPTM.Research interestsincludethefunctionalizationofnanomaterialsandtheirapplicationinenergystorage,catalysis,and biomedicine.Resultshavebeenpublishedinmorethan120articles(h-index38,Scopus),and istheprincipalinvestigatorinseveralEuropeanprojects. Adv. Energy Mater. 2024,14, 2400521 2400521 (51 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License www.advancedsciencenews.com www.advenergymat.de Shashank Sundriyal isa MarieSkłodowska-CurieIndividualPostdoctoralFellowintheCzechAdvancedTechnologyandResearchInstitute(CATRIN,Palacky UniversityOlomouc).Hereceivedhis Ph.D.from theAcademyofScientificandInnovativeResearch(AcSIR-CSIO),Chandigarhin2019. Hisresearch interestsembracethesynthesisofmetal–organicframeworks,graphene,biomassderivedcarbons, andcompositesforenergystorageapplications.Hehaspublishedmorethan48 articles(2078citations,h-index22)inreputedinternationaljournals.HeisthewinnerofseveralprestigiousinternationalfellowshipsandawardsincludingGreenTalents2021Germany,MSCAco-funded PASIFIC2021 Poland,MSCAA-PF2021,andFulbrightNehru2022UnitedStates. Adv. Energy Mater. 2024,14, 2400521 2400521 (52 of 52) © 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH 16146840, 2024, 24, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400521 by Technical University Ostrava, Wiley Online Library on [06/12/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License