Regula A icle
The dynamic e hylene adso p ion on ca bon xe ogels as a h ee-way game
be ween po osi y, su ace chemis y and humidi y
Lo ena T. P´
e ez-Poya os , Se gio Mo ales-To es
*
, Luisa M. Pas ana-Ma ínez ,
F ancisco J. Maldonado-H´
oda
NanoTech – Nanoma e ials and Sus ainable Chemical Technologies, Depa men o Ino ganic Chemis y, Facul y o Sciences, Uni e si y o G anada, A da. Fuen e Nue a
s/n, ES18071 G anada, Spain
GRAPHICAL ABSTRACT
ARTICLE INFO
Keywo ds:
Ca bon xe ogels
Su ace chemis y
Po osi y
Hyd ophobici y
Dynamic adso p ion
E hylene
ABSTRACT
No el ca bon xe ogels doped wi h he e oa oms (O, N, S) we e p epa ed by sol–gel polyme iza ion o eso cinol
wi h he e ocyclic aldehydes con aining hem. All doped ma e ials p esen ed highe O-con en s han he e e ence
ma e ial p epa ed wi h o maldehyde, and signi ican S- o N-loadings in he co esponding samples. Ca bon
xe ogels we e mic o-mesopo ous and N-doping a ou ed he o ma ion o mesopo es. Thei e iciency in he
dynamic e hylene adso p ion is p esen ed as an in e play be ween po osi y, su ace chemis y and humidi y. The
su ace hyd ophilici y was also s udied by wa e adso p ion assays, a quick adso p ion being a ou ed in
mic opo ous samples wi h hyd ophilic O-g oups. B eak h ough cu es o e hylene adso p ion we e eco ded in
bo h d y and humid condi ions and analysed acco ding o he mass ans e ence zone (MTZ). The ma e ial
beha iou was co ela ed wi h he physicochemical p ope ies, eluci a ing he mechanism o he simul aneous
wa e /e hylene adso p ion. The adso p ion capaci y depended linea ly on he mic opo ous cha ac e is ics o
samples; howe e , MTZ pa ame e s (e iciency o he column) a ied linea ly wi h he elec onega i i y o he
dopan elemen . Bo h doping and humidi y in he s eam hinde ed he e hylene adso p ion kine ic and capaci y
(up o 33% o N-doped ma e ial unde humidi y compa ed o undoped-ma e ial unde d y condi ions), due o
educed adso ba e-adso ben in e ac ions and he accessibili y in o na ow po es.
* Co esponding au ho .
E-mail add ess: [email p o ec ed] (S. Mo ales-To es).
Con en s lis s a ailable a ScienceDi ec
Jou nal o Colloid And In e ace Science
jou nal homepage: www.else ie .com/loca e/jcis
h ps://doi.o g/10.1016/j.jcis.2024.08.044
Recei ed 6 June 2024; Recei ed in e ised o m 27 July 2024; Accep ed 7 Augus 2024
Jou nal o Colloid and In e ace Science 678 (2025) 480–493
A ailable online 10 Augus 2024
0021-9797/© 2024 The Au ho (s). Published by Else ie Inc. This is an open access a icle unde he CC BY-NC-ND license ( h p://c ea i ecommons.o g/licenses/by-
nc-nd/4.0/ ).
1. In oduc ion
In o de o make ui and ege ables a ailable ou side ha es ing
season, i is necessa y o handle and p ese e hem p ope ly. Among
hem, he managemen o he so-called climac e ic p oduc s (e.g., ap-
ples, pea s, kiwis, a ocados, oma oes, e c.) should be ca e ully
con olled because he ma u a ion o he ui s con inues once ha -
es ed, in con as o non-climac e ic p oduc s [1]. This p ocess is ca -
ied ou wi h he na u al elease o e hylene (C
2
H
4
), among o he gases,
om he s o ed ui s. E hylene plays an impo an ole as a ho mone o
ipening, s imula ing he espi a ion and he ans o ma ion o some
o ganic compounds (suga s), esponsible o changes in colou and
la ou . E en a e y low concen a ions (0.1 µL/L), e hylene may cause
o e ipe, quick de e io a ion and senescence, sho ening he p oduc s’
shel li es and consequen ly, leading o huge economic losses o he
ag icul u al sec o [2,3].
Fo his eason, i is c i ical o con ol anspo a ion and s o age
condi ions. Reducing empe a u e and limi ing oxygen a ailabili y a e
adi ional measu es aken o slow down he ipening p ocess. Thus,
s o age and anspo a ion a e ca ied ou in cold chambe s unde
con olled a mosphe es (low o ul alow oxygen con en , high humidi y
and CO
2
le els) o p ese e ui quali y. On he o he hand, e hylene
concen a ion should be kep as low as possible using di e en ap-
p oaches. The i s op ion is he use o chemical inhibi o s which block
he p oduc ion cen es (i.e., 1-me hylcyclop opene – 1-MCP), o a oid
he e hylene elease by coa ing ui s wi h waxes [4]. Al e na i ely, he
e hylene o med may be emo ed o ans o med in o inac i e mole-
cules. New packaging sys ems ha e been de eloped o his pu pose,
such as pe meable bags illed wi h adso ben s o s ong oxidan s ha a e
included in he packaging. In pa icula , po assium pe mangana e
(KMnO
4
) was used as e hylene sca enge , o oxidize i o CO
2
and H
2
O o
a ce ain ex en [5]. Ozone was also p oposed as al e na i e oxidan [3].
Howe e , bo h chemical me hods ha e d awbacks associa ed o he
limi ed e iciency o e hylene emo al and he oxici y o he com-
pounds used, which could en ail some isks o ood sa e y. The e o e,
he de elopmen o no el, non-haza dous and sus ainable al e na i es
o e hylene emo al is o g ea in e es o he ag o- ood indus y. The
e hylene emo al by speci ic adso ben s is cu en ly eme ging as one o
he mos p omising and economically compe i i e echnologies [6,7].
Some o he ma e ials commonly used include zeoli es, silica, clays o
ca bon ma e ials [6]. Howe e , some s udies e ealed ha ca bon-based
ma e ials possess a highe s uc u al and chemical s abili y, lowe cos
and be e hyd ophobici y han he es o adso ben s, which has u ned
hem in o con enien e hylene adso ben ma e ials [8–10].
The adso p i e capaci y o ca bon ma e ials depends on he combi-
na ion o ac o s, such as ex u al p ope ies and su ace chemis y, so
he ideal scena io would be o de elop ma e ials wi h uneable physi-
cochemical p ope ies. Ca bon xe ogels ha e eme ged as pe ec can-
dida es o his pu pose, because bo h aspec s can be con olled by
i ing he syn hesis p ocess [11]. The syn hesis o hese ma e ials was
de eloped by Pekala e al. in he ea ly 1990 s [12] and i is a wo-s ep
eac ion me hod in ol ing he hyd olysis and condensa ion o he p e-
cu so s. The i s wo ks in his line we e based on he aqueous (W)
polyme iza ion o eso cinol (R) and o maldehyde (F) ca alysed (C) by
weak bases (Na
2
CO
3
), highligh ing ha many a iables mus be ca e-
ully adjus ed, as hey g ea ly a ec he p ope ies o he inal ma e ial.
The wide ange o a iables, such as he eso cinol/ o maldehyde a io,
pH o he solu ion, d ying p ocess o empe a u e and du a ion o he
ca boniza ion s ep, while inc easing he di icul y o ep oducing he
samples, should be conside ed as a powe ul ool o adjus he p ope ies
o he syn hesized ma e ial o he speci ic equi emen s o an applica-
ion. On his p emise, he syn hesis me hod has been ex ensi ely
modi ied o adjus he po osi y, su ace chemis y, mechanical p ope -
ies o mic o- o mac o-s uc u e o ca bon gels [13]. One o he ap-
p oaches o adjus he chemical su ace o he xe ogels is based on he
use o di e en c oss-linke monome s, such as melamine [14], phenol
[15], u u al [16], phlo oglucinol [17], e c., achie ing ca bon ma e ials
doped wi h di e en he e oa oms in hei s uc u e. The in oduc ion o
hese he e oa oms gene a es new unc ional g oups and ac i e cen es
wi h di e en elec onega i i y on he suppo s, hus modi ying su ace
a ini y o he ca bon ma e ial o speci ic adso ba es [18–21], such as
me hane [13], oluene [22], ace one [22,23], o e hylene [24], as VOC
examples.
Based on he commen ed e sa ili y o he sol–gel p ocedu e o ailo
he cha ac e is ics o ca bon gels, we syn hesized ca bon gels doped wi h
di e en he e oa oms (i.e., O, S and N) using he e ocyclic aldehydes
con aining hese elemen s as ca bon p ecu so s. These no el ca bon
xe ogels wi h a ailo ed mic osphe e s uc u e and speci ic composi ion
we e syn hesized o elucida e he ole o po osi y and su ace chemis y
when de eloping e icien and selec i e e hylene adso ben s. The
physicochemical p ope ies, including hyd ophobici y, we e analysed
using complemen a y cha ac e iza ion echniques and ela ed o he
pe o mance o he samples in he elimina ion o e hylene om gaseous
s eams by adso p ion unde di e en condi ions (mainly, in he p es-
ence o absence o humidi y). To he bes o ou knowledge, his is he
i s s udy ex ensi ely dealing wi h he in luence o he chemical su ace
and po osi y o ca bon xe ogels and he p esence o mois u e on he
s eam, on e hylene emo al by adso p ion in dynamic condi ions.
2. Ma e ials and me hods
2.1. Chemicals
N-hep ane (C
7
H
16
, 99.8 %, VWR Chemicals), Span® 80 (C
26
H
50
O
7
,
>60 %, Sigma Ald ich), me hanol (CH
3
OH, >99.9 %, VWR Chemicals),
eso cinol (C
6
H
6
O
2
, 99 %, Al a Aesa ), o maldehyde (CH
2
O, 37 %,
Sigma Ald ich), hiophene-2-ca boxaldehyde (C
5
H
4
OS, 98 %, The mo
Scien i ic), py ole-2-ca boxaldehyde (C
5
H
5
NO, 98 %, Apollo Scien i-
ic), u u al (C
5
H
4
O
2
, 98 %, Me ck), hyd ochlo ic acid (HCl, 37 %,
Labkem), ace one (C
3
H
6
O, >99 %, VWR Chemicals) and C
2
H
4
/He cyl-
inde (1000 ppm o 0.1 % C
2
H
4
in He, Ai Liquide).
2.2. Syn hesis o he e oa om-doped ca bon xe ogels
Samples we e p epa ed in a s i ed ba ch eac o consis ing o a
h ee-neck ound-bo om lask equipped wi h a e lux, mechanical s i -
ing and empe a u e con olle . Fo he syn hesis o he e e ence RF
o ganic gel, 450 mL o n-hep ane as eac ion media, 11 mL o Span® 80
(a non-ionic su ac an ) and a i ed Milli-Q aqueous solu ion o R, we e
hea ed up o 75 ◦C unde s i ing and e lux. Then, he app op ia e
amoun o F solu ion was d opped on he p ehea ed solu ion. To p epa e
o ganic doped gels, he e oa oms we e in oduced di ec ly in he chem-
ical polyme ic ne wo k by eplacing F wi h he co esponding aldehyde,
namely hiophene-2-ca boxaldehyde o gene a e S- unc ionali ies,
py ole-2-ca boxaldehyde o N- unc ionali ies, and u u al o inc ease
he O-con en , which we e p e iously dissol ed in me hanol. All ecipes
main ain a R/aldehyde mola a io o 1/2 and a R/W mola a io o 1/8.
Finally, 4 mL o HCl we e added d op by d op o he suspension, aging
he polyme o 24 h o gua an ee comple e condensa ion. A e wa d,
he o ganic gels we e il e ed and washed wi h abundan ace one o
emo e es o sol en s and un eac ed p oduc s and s o ed in ace one
suspension o 24 h, enewing ace one a e each 8 h. This allows he
exchange o sol en s by illing he po es wi h ace one, which conside -
ably educes he sh inkage o he po osi y du ing he d ying p ocess
[25,26]. A e sol en exchange, samples a e eco e ed by il e ing,
d ied o e nigh a 80 ◦C o comple ely e apo a e he ace one, and s o ed
in a desicca o o p e en humidi y adso p ion. The gels ob ained we e
la e ca bonized in an o en unde N
2
a mosphe e a 800 ◦C wi h a soak
ime o 1 h and a hea ing a e o 3 ◦C/min. This ca boniza ion empe -
a u e was chosen o p o ide high he mal, mechanical and s uc u al
s abili y o he inal p oduc s. In gene al, he py olysis o o ganic gels is
comple e a a ound 700 ◦C [12,27].
L.T. P´
e ez-Poya os e al.
Jou nal o Colloid And In e ace Science 678 (2025) 480–493
481
The samples we e labelled as A-XG, whe e “XG” deno es xe ogel
cha ac e (subc i ical d ying); and “A” e e s o he aldehyde used
du ing he e oa om-doping, i.e., “O” (oxygen) o u u al, “S” (sulphu )
o hiophene-2-ca boxaldehyde and “N” (ni ogen) o py ole-2-
ca boxaldehyde, while “C” co esponds o he e e ence xe ogel p e-
pa ed wi h F. Thus, he ca bon xe ogels C-XG ( e e ence), S-XG, N-XG
and O-XG we e ob ained.
2.3. Cha ac e iza ion echniques
Di e en complemen a y echniques we e used o cha ac e ize he
samples. The mo phology o he adso ben s was s udied by scanning
elec onic mic oscopy (SEM), wi h a high- esolu ion mic oscope Ca l
Zeiss SMT, model Au iga. Elemen al analysis (EA) was ca ied ou o
de e mine he bulk chemical composi ion o samples using a The mo
Scien i ic, model Flash 2000 equipmen . The mog a ime ic analysis
(TGA) was pe o med o de e mine he he mal s abili y o he ma e ials
unde ai a mosphe e (hea ing up o 800 ◦C and wi h a hea ing a e o
5 ◦C/min) using a SHIMADZU TGA-50H he mobalance. The iden i i-
ca ion o chemical g oups was ca ied ou by a enua ed o al e lec ance
coupled wi h Fou ie T ans o m in a ed spec oscopy (ATR-FTIR) and
X- ay pho oelec on spec oscopy (XPS) analysis, eco ded espec i ely
wi h a JASCO 6200 and a K a os Axis Ul a-DLD o de e mine he na u e
and pe cen age o each chemical species on he su ace. Su ey and
mul i- egion spec a we e eco ded a C1s, O1s, S2p and N1s pho o-
elec on peaks and each spec al egion was scanned se e al imes o
ob ain good signal- o-noise a ios. The poin o ze o cha ge (pH
PZC
) o
he samples was de e mined acco ding o he p ocedu e de eloped by
Leon [28,29]. The con en o acidic and basic su ace unc ional g oups
in he ca bon xe ogels has been de e mined using Boehm i a ion [30].
In a ypical assay, 0.10 g o sample was suspended in sepa a e lasks
con aining 10 mL o HCl 0.10 M, NaOH 0.10 M, Na
2
CO
3
0.05 M and
NaHCO
3
0.10 M. The suspensions we e le shaking o 48 h and hen,
hey we e il e ed, and 5 mL o each solu ion we e i a ed wi h HCl 0.10
M o NaOH 0.10 M. The ex u al pa ame e s o he samples we e ob-
ained using N
2
and CO
2
physical adso p ion a –196 ◦C and 0 ◦C,
espec i ely, wi h a Quad aso b SI equipmen (Quan ach ome). Fo
ha , he samples we e ou gassed o 12 h a 110 ◦C wi h a high acuum
o 10
–6
mba . B unaue , Emme and Telle (BET) me hod was applied o
calcula e he appa en su ace a ea (S
BET
) o he samples [31]; Dubinin-
Radushke ich (DR) equa ion was used o calcula e he mic opo e ol-
ume (W
0
) o he samples [32,33], while S oeckli equa ions [34] we e
applied o de e mine he mic opo e su ace a ea (S
mic o
) and mean
mic opo e wid h (L
0
). To al po e olume (V
T
) was conside ed as he
olume o N
2
adso bed a a ela i e p essu e (P/P
0
) o 0.95, which is due
o he olume o mic o- and mesopo es acco ding o Gu ich’s ule
[33,35]. The Ba e , Joyne and Halenda (BJH) me hod [36] and
quenched solid densi y unc ional heo y (QSDFT) we e used o calcu-
la e he po e size dis ibu ion (PSD) [37,38]. The hyd ophobici y o he
ca bon xe ogels was de e mined using a g a ime ic me hod, which
es ima es he amoun o wa e apo adso bed in o he samples a oom
empe a u e and 100 % ela i e humidi y (RH), unde s a ic condi ions
un il a cons an weigh (sa u a ion) is achie ed.
2.4. E hylene adso p ion assays
E hylene adso p ion was pe o med in dynamic condi ions using
glass eac o s con aining a ound 0.40 g o adso ben s sie ed unde 150
µm, which o m a ixed bed o 8.0 ×0.60 cm. The expe imen s a e
ca ied ou a a mosphe ic p essu e wi h a o al low o 25 cm
3
/min o a
mix u e o N
2
/O
2
/C
2
H
4
/H
2
O. The i ed C
2
H
4
concen a ion in he
syn he ic ai mix u e (21 % O
2
) was 100 ppm , while he in luence o
humidi y was analysed by pe o ming addi ional expe imen s in d y
condi ions o a 50 % RH. Adso p ion expe imen s we e ca ied ou o
ob ain he b eak h ough cu es [39–41]. The mix u e passed h ough
he columns, and he e hylene and wa e exi ing he ou le end o he
column we e analysed using a gas ch oma og aph (Shimadzu GC 2010
Plus), equipped wi h R -Msie e 5A and R -Q-BOND columns, and a
ba ie discha ge ioniza ion (BID) de ec o .
The amoun o e hylene adso bed in he b eak h ough (X
0.02
) and
sa u a ion poin s (X
0.90
) a e compa ed. These poin s a e de ined as he
ime on s eam o he elu ed olume be o e he C
2
H
4
concen a ion
measu ed a he ou le end o he column eached 2 % and 90 % o he
ini ial concen a ion, espec i ely. Ano he impo an pa ame e is he
heigh o he mass ans e zone (H
MTZ
), ep esen ing he egion o he
ixed bed in which adso p ion is aking place, calcula ed ollowing he
equa ions (Eqs. (1)–(2):
HMTZ =h(V0.90 −V0.02
V0.02+ϕ(V0.90 −V0.02))(1)
ϕ=∫V0.90
V0.02 (C0−C)dV
C0(V0.90 −V0.02)(2)
in which “h” is he heigh o he adso p ion bed and “ϕ”, he ac ional
capaci y, which e alua es he e iciency o he adso p ion p ocess. Since
H
MTZ
p og essi ely mo es along he column as he adso ben is sa u-
a ed, R
MTZ
is de ined as he a e o ad ance o H
MTZ
h ough he ixed
bed eac o , acco ding o Eq. (3):
RMTZ =HMTZ/( 0.90 − 0.02)(3)
3. Resul s and discussion
3.1. Physicochemical cha ac e iza ion
The i s objec i e was o alida e he success o he syn hesis p ocess
in gene a ing s able chemical g oups a e ca boniza ion a 800 ◦C. The
bulk and su ace chemical composi ion o he samples we e ob ained by
EA and XPS, espec i ely (Table 1). The C-XG sample syn hesized om
he classical RF mix u e was chosen as e e ence ma e ial. The inc eased
O, N and S con en s, acco ding o he monome used in each syn hesis,
con i m he iabili y o he designed p ocedu e. Thus, he applied one-
po sol–gel me hod e ec i ely gene a es s able chemical g oups on
ca bon xe ogels, making i an easy unc ionaliza ion ool. Oxygen and
ni ogen unc ionali ies seem o be mo e homogeneously dis ibu ed
a e ca boniza ion a 800 ◦C han he sulphu ones, showing a signi i-
can educ ion o he su ace S-con en ega ding he bulk concen a ion
(i.e., 1.3 % s. 4.3 % o S
XPS
and S
EA
, espec i ely). All ma e ials p e-
sen ed sligh ly basic pH
PZC
alues (Table 1). Inc easing he O-con en
ypically inc eased he concen a ion o oxygen-con aining su ace
g oups, such as anhyd ide o ke ones (ca boxylic acids p esen a low
he mal s abili y) wi h acidic cha ac e . Ne e heless, he e is only a
weak acidi ica ion o O-XG ega ding he e e ence C-XG. On he con-
a y, N- unc ionali ies enhanced he basic cha ac e , al hough again,
he inc ease in pH
PZC
is also mode a e.
The he mal s abili y o he ca bon xe ogels unde ai a mosphe e
was s udied using TGA (Fig. S1). All ma e ials we e s able below 200 ◦C,
he mass loss (a ound 5 w %) a his empe a u e being p obably ela ed
o emo al o adso bed humidi y. The combus ion a e mainly inc eased
abo e 400 ◦C. The simila p o ile o he TGA cu es deno es he high
s abili y o he di e en unc ional g oups ega dless he he e oa om
elemen . These g oups emain s able a e ca boniza ion unde ni ogen
a mosphe e a 800 ◦C, hus inducing only small di e ences be ween he
s abili y o he samples when analyzed unde oxidan condi ions.
The mo phology o he ma e ials was analysed by SEM. In gene al,
he s uc u e o he o ganic gels was composed o mic osphe es, induced
by he s i ing mo emen inside a sphe ical eac o and he p esence o
he su ac an in he s a ing solu ion. As obse ed in Fig. 1a, he C-XG
ca bon xe ogel is o med by mic osphe es wi h a mean size a ound 20
μ
m. De ails o he mic osphe es’ su ace (Fig. 1b) deno e ha hey a e
also o med by smalle mic osphe es wi h a mean diame e o ~0.2 µm
L.T. P´
e ez-Poya os e al.
Jou nal o Colloid And In e ace Science 678 (2025) 480–493
482
(Fig. 1c), ypically e e ed o as “p ima y pa icles”. In gene al,
he e oa om-doped ca bon xe ogels main ained he sphe ical mic o-
s uc u e, al hough wi h some modi ica ions. The di e en aldehydes
used in he syn hesis modi ied he size and o e lapping deg ee o he
p ima y pa icles (Fig. 1d– ), esul ing in a smalle size (a ound 0.1 µm)
and a la ge o e lapping deg ee, c ea ing di e en opened po osi y
(meso- and mac opo e dis ibu ion) be ween he p ima y pa icles.
Tex u al p ope ies o samples a e closely ela ed wi h he p e iously
Table 1
Poin o ze o cha ge (pH
PZC
), and bulk and su ace chemical composi ion (w %) o he e oa om-doped ca bon xe ogels de e mined by EA and XPS, espec i ely.
Sample C
EA
(%)
O
EA
*
(%)
N
EA
(%)
S
EA
(%)
H
EA
(%)
C
XPS
(%)
O
XPS
(%)
N
XPS
(%)
S
XPS
(%)
pH
PZC
C-XG 87.9 7.3 − − 4.8 96.2 3.8 − − 7.4
O-XG 81.7 13.2 − − 5.1 90.5 9.5 − − 7.1
S-XG 83.1 8.4 −4.3 4.2 92.6 6.1 −1.3 7.3
N-XG 79.5 9.8 6.4 −4.3 88.7 5.8 5.5 −7.8
*
Calcula ed by di e ence.
Fig. 1. SEM mic og aphs o (a-c) e e ence C-XG and (d- ) he e oa om-doped ca bon xe ogels: (a, b) mic osphe es size and (c- ) dis ibu ion o p ima y pa icles.
L.T. P´
e ez-Poya os e al.
Jou nal o Colloid And In e ace Science 678 (2025) 480–493
483
desc ibed mo phology. Thus, he PSD o samples ob ained by sol–gel
p ocedu es depends on he combina ion o nume ous p ocesses ca ied
ou du ing syn hesis. The polyme iza ion s ep de ines he shape,
dimension and o e lapping o p ima y pa icles o ming he 3D-
ne wo k, which basically de ine he mesopo ous ange. In con as ,
he hea ea men condi ions de e mine he py olysis deg ee and he
elease o gases, which in u n, de elop he mic opo osi y [25,26]. The
sh inkage unde gone du ing hese p ocesses is ela ed no only wi h he
selec ed d ying me hod o ca boniza ion condi ions, bu also wi h he
mechanical p ope ies o he samples [25,42].
The ex u al cha ac e iza ion o he samples was ca ied ou by
de e mining he complemen a y adso p ion iso he ms o N
2
and CO
2
(Fig. 2a and b). The ex u al pa ame e s ob ained om he analysis o
hese iso he ms, acco ding o he p ocedu es desc ibed in he expe i-
men al sec ion, a e lis ed in Table 2. The N
2
adso p ion–deso p ion
iso he ms o ca bon xe ogels (Fig. 2a) belong o ype I and IV o he
IUPAC classi ica ion. In ac , only he iso he m o N-XG is mainly a ype
IV iso he m, cha ac e is ic o mesopo ous ma e ials. These p o iles
deno e he hie a chical PSD o ma e ials, combining he in insic
mic opo ous na u e o he samples wi h he p esence o some meso-
po es. A a glance, i is obse ed ha all doped ca bon xe ogels p esen a
lowe po osi y (V
T
) han he e e ence ma e ial, excep in he case o N-
XG. The N
2
adso p ion a low ela i e p essu e (P/P
0
) is always smalle
han o he e e ence sample, his dec ease being especially no o ious
o N-XG, deno ing a lowe mic opo osi y (Fig. 2a). Mo eo e , he wide
neck obse ed in he iso he ms o S-XG and mainly, O-XG samples,
sugges he o ma ion o a mo e he e ogeneous mic opo osi y in hese
samples. A P/P
0
>0.4, he slope o he cu es and he hys e esis loop
deno e he p esence o mesopo es in all cases. The hys e esis loop is in
gene al o ype H4, wi h excep ion o N-XG, ha becomes ype H3, bo h
ela ed wi h sli -shaped po es. As no e, he slope o he iso he ms p o-
g essi ely inc eased in he end S-XG<O-XG<C-XG<N-XG, indica ing
an inc eased mesopo osi y in his sense. Fo he N-XG sample, he deep
inc ease o he amoun adso bed om P/P
0
>0.8 deno es he p esence
o la ge mesopo es han in he es o samples. Simul aneously, he H3
hys e esis cycle also implies a deepe in luence o he mic opo ous ange
on he condensa ion/e apo a ion o N
2
[14,43]. Thus, N-XG should
p esen a well-de eloped mesopo osi y o med by la ge mesopo es, bu
a educed mic opo osi y consis ing o la ge mic opo es.
The ex u e analysis o he samples is co obo a ed by de e mining
he PSD by QSDFT and BJH me hods, which a e in good ag eemen
(Fig. 2c and d). QSDFT con i ms ha , in gene al, samples a e mainly
mic opo ous (Fig. 2c). I is no ewo hy ha he e e ence ca bon xe ogel
(C-XG) p esen s he na owes mic opo osi y bu also a ce ain con i-
bu ion o mesopo es wi h a diame e o a ound 3 nm. As expec ed, la ge
mesopo es wi h a diame e a ound 13 nm we e ound o he meso-
po ous N-XG, in good ag eemen wi h he alue o 17 nm de ec ed by
BJH me hod (Fig. 2d). Bo h me hods also con i m he sca ce mesopo ous
cha ac e o bo h S-XG and O-XG samples.
A deepe cha ac e iza ion o he mic opo osi y was ca ied ou by
applying DR and S oeckli (DR-S) equa ions o he N
2
adso p ion da a
(Table 2). As expec ed, he e oa om-doping educes he mic opo e ol-
ume (W
0
) o he samples, bu L
0
alues s ongly inc eased ega ding he
e e ence ma e ial. The mesopo ous olume (V
meso
) also dec eased, wi h
excep ion o N-XG. The lowe po osi y o he he e oa om-doped gels is
also e i ied by a dec eased su ace a ea. In ac , when compa ing S
BET
and S
mic o
om N
2
iso he m da a, simila alues we e ob ained only o
C-XG. In he he e oa om-doped gels, S
BET
is always highe han S
mic o
,
and he dec ease o su ace by doping is la ge o S
mic o
alues han o
S
BET
, poin ing ou ha he s onge ans o ma ions ake place a he
mic opo e ange.
The CO
2
adso p ion o he samples complemen s he cha ac e iza ion
o mic opo osi y, allowing a mo e de ailed analysis o he na owes
mic opo osi y (diame e <0.7 nm). Compa ing he CO
2
iso he ms
Fig. 2. Adso p ion iso he ms o (a) N
2
and (b) CO
2
o he di e en ca bon xe ogels. PSD ob ained by applying (c) QSDFT and (d) BJH me hod o he N
2
adso p ion da a.
L.T. P´
e ez-Poya os e al.
Jou nal o Colloid And In e ace Science 678 (2025) 480–493
484
(Fig. 2b), i is obse ed ha he na ow mic opo osi y is a ou ed in O-
XG, and deeply educed in he mesopo ous N-XG ca bon xe ogel,
ega ding he e e ence ma e ial. Inc easing he oxygen con en in he
3D-s uc u e o he aw o ganic xe ogel by using u u al, a highe CO
x
elease a ou ed he de elopmen o na ow mic opo es and he eby,
S
mic o
. On he con a y, py ole-2-ca boxaldehyde educed he mic o-
po osi y in all anges (W
CO2
and W
N2
), and consequen ly, N-XG p e-
sen ed he smalles su ace a ea, despi e he high V
meso
de eloped.
Meanwhile, hiophene-2-ca boxaldehyde exhibi s an in e media e
beha iou ; in his case, he la ge educ ion ega ding he e e ence
sample akes place in he mesopo e ange. Thus, he di e en monome s
used du ing he e oa om-doping en ail signi ican changes in he ex u al
pa ame e s o he samples, as p e iously epo ed [44–46]. As a gene al
commen , bo h S
mic o
and W
0
de e mined om CO
2
adso p ion we e
always highe han hose ob ained om N
2
adso p ion, hus deno ing
he N
2
-di usion es ic ion o he na owes mic opo osi y. This ac is
clea ly poin ed ou when compa ing he S
mic o
(CO
2
)/S
mic o
(N
2
) a io,
which s ongly inc eased a e doping, mo e ma kedly in he case o he
mesopo ous N-doped sample (Table 2). As no e, mesopo ous ma e ials
p esen he s onges di usion p oblems o he en ance o he mic o-
po osi y, despi e he la ge mic opo e size (L
0
).
The adso p i e beha iou o samples will be in luenced by bo h
ex u al and chemical cha ac e is ics. Thus, oge he wi h he ex en and
accessibili y o he su ace (PSD), he dis ibu ion and concen a ion o
chemical g oups on hese su aces de e mine he s eng h o he in-
e ac ions wi h a speci ic adso ba e. The main su ace unc ionali ies
inco po a ed in he samples was s udied by ATR-FTIR (Fig. 3). In gen-
e al, he in ensi y o he FTIR bands in he doped samples inc eases
ega ding he e e ence ma e ial. These bands we e assigned acco ding
o he li e a u e [47–49]. Speci ically, he b oad band in he egion
be ween 3700–3100 cm
−1
obse ed in all samples was assigned o
–
OH
s e ching ib a ions, also o e lapping in he N-doped sample wi h he
ib a ion o e minal
–
NH g oups. In he egion o 2800–2900 cm
−1
,
wo peaks a 2850 cm
−1
and 2920 cm
−1
we e assigned o symme ic and
asymme ic CH
2
alipha ic s e ching ib a ions. These bands a e
signi ican ly mo e in ense o S-XG, deno ing he p esence o alipha ic
s uc u es and, p obably, a smalle a oma ic cha ac e . Howe e , no
signal o he –SH s e ching peak is obse ed a 2570 cm
−1
o his
sample. In he egion o ~1700 cm
−1
, he oxygena ed su ace g oups a e
de ec ed, he peak a ~1740 cm
−1
being assigned o he ca bonyl C
–
–
O
s e ching o ca boxylic, anhyd ides o lac onic s uc u es [49]. I is
no ewo hy he di e en dis ibu ion o oxygena ed su ace g oups in
he samples, since his band is no obse ed in O-XG and N-XG samples,
in which he band a ~1600 cm
−1
is ein o ced. The signals in he egion
1500–1600 cm
−1
a e associa ed wi h conjuga ed C
–
–
C bonds. The C
–
–
C
ib a ion in a oma ic ings was assigned a ~1590 cm
−1
, while C
–
–
C in
condensed a oma ic ings was designa ed a ~1550 cm
−1
, he la e
a ou ed in he case o N-XG. In he 1000–1300 cm
−1
egion, mul iple
and o e lapped weak bands due o C
–
O (phenols, alcohols o e he
b idges be ween ings) and C
–
N bonds a ~1250 cm
−1
o N
–
CH
3
bonds
a ~1372 cm
−1
we e also p e iously epo ed [48].
High esolu ion XPS spec a o he C1s (Fig. 4a, b) and O1s (Fig. 4c– )
egions we e analysed, oge he wi h he signals o he co esponding
S- o N-doping elemen , i.e., S2p (Fig. 4g) o N1s egions (Fig. 4h),
espec i ely. The na u e and concen a ion o chemical species om
decon olu ion o each speci ic spec al egion we e assigned acco ding
o he li e a u e [39,50], and a e summa ized in Table S1 o he
Supplemen a y Ma e ial. The decon olu ion o he C1s egion (Fig. 4a
and b) was ca ied ou using ou componen s assigned as ollows:
C
–
C (284.6 eV); C
–
O (~285 eV); C
–
–
O (~286 eV) and O
–
C
–
–
O
(~289 eV). As obse ed, all he e oa om-doped ca bon xe ogels showed
an inc eased su ace O-con en (Table 1). The C1s p o ile o S-XG was
compa able o ha o he e e ence sample, p obably associa ed wi h a
low S-con en in su ace. On con as , he C1s p o ile o N-XG is
signi ican ly wide and shows a slowe decay, which con i ms he C
–
N
unc ionaliza ion. The peaks co esponding o C
–
O bonds and C
–
N o
C
–
S bonds o e lap be ween hem, leading o la ge ails on he co e-
sponding spec a.
Two componen s we e no mally used o i he decon olu ion o he
high- esolu ion O1s spec a, o he ca bon ma e ials (Fig. 4c– ), assigned
as C
–
–
O and C
–
O bonds a ~531.5 eV and ~533.0 eV, espec i ely
[39]. In he case o he e oa om-doped ca bon xe ogels, he O1s p o ile
signi ican ly enla ged, indica ing he o ma ion o addi ional su ace
g oups, in which oxygen is linked o hese he e oa oms. Thus, new
componen s a ~532.3 eV and ~534.6 eV, associa ed wi h S
–
O and
N
–
O bonds [45,50], we e included o i he decon olu ion o O1s e-
gion o S-XG and N-XG, espec i ely. The na u e o N- and S-con aining
g oups was mo e speci ically de e mined by analysing he S2p o N1s
spec al egions. In his con ex , he decon olu ion o he S2p egion,
wi h a ypical peak spli ing o 1.2 eV be ween S2p
3/2
and S2p
1/2
, o S-
XG is shown in Fig. 4g. The main con ibu ion obse ed a ~163.9 eV
co esponds o C
–
S
–
C s uc u es, such as hose exis ing in he aw
hiophene-2-ca boxaldehyde, co obo a ing i s inco po a ion in he 3D-
ne wo k s uc u e. In addi ion, o he smalle componen s we e assigned
Table 2
Tex u al pa ame e s o he he e oa om-doped ca bon xe ogels.
Sample N
2
adso p ion CO
2
adso p ion S
mic o
CO
2
/ S
mic o
N
2
S
BET
(m
2
/g) V
T
(cm
3
/g) V
meso
(cm
3
/g) W
0
(cm
3
/g) L
0
(nm)
S
mic o
(m
2
/g)
W
0
(cm
3
/g)
L
0
(nm) S
mic o
(m
2
/g)
C-XG 545 0.35 0.11 0.23 0.82 555 0.26 0.57 905 1.6
O-XG 495 0.30 0.07 0.21 1.26 288 0.37 0.60 1108 3.8
S-XG 444 0.22 0.03 0.18 1.70 223 0.25 0.66 823 3.7
N-XG 254 0.44 0.30 0.11 1.86 115 0.16 0.61 630 5.5
S
BET
=BET su ace a ea; V
T
= o al po e olume; V
meso
=mesopo ous olume; W
0
=mic opo e olume; L
0
=mean mic opo e wid h; S
mic o
=mic opo ous su ace a ea;
S
mic o
CO
2
/N
2
=mic opo ous su ace a ea a io ob ained om CO
2
and N
2
iso he m da a.
Fig. 3. ATR-FTIR spec a o he e e ence and he e oa om-doped ca -
bon xe ogels.
L.T. P´
e ez-Poya os e al.
Jou nal o Colloid And In e ace Science 678 (2025) 480–493
485
a ~164.4 eV and ~167.5 eV, associa ed o H
–
S
–
C and oxidized
sulphu moie ies (e.g., sul ones, sul ona es o sulpha es), espec i ely
[44,45]. The decon olu ion o he N1s egion o N-XG (Fig. 4h) shows
ou componen s associa ed o py idinic N6 (~398.7 eV), py olic N5
(~400.0 eV), qua e na y N (~401.4 eV) and oxidized ni ogen species
(N ox) (~402.5 eV) [50]. The main componen was he one due o
qua e na y ni ogen g oups, which should also jus i y he inco po a ion
o he aw chemical compound o he N-XG s uc u e du ing he
syn hesis.
The concen a ion o basic and acidic su ace g oups c ea ed in he
di e en ca bon xe ogels was de e mined by Boehm i a ion, and he
esul s a e shown in Table 3. Acco ding o his p ocedu e, i a ion wi h
HCl o NaOH was used o de e mine he o al basic and acid unc ionali ies,
espec i ely. The dis ibu ion o acid si es is analysed, by compa ison, wi h
he esul s ob ained by i a ion wi h Na
2
CO
3
, which de e mines ca box-
ylic acid g oups and lac ones, ega ding NaHCO
3
, only able o i a e
ca boxylic acid g oups. These esul s a e in good ag eemen wi h he
e olu ion o he pH
PZC
alues (Table 1), as well as wi h he a ia ion o
he chemical composi ion de e mined by bo h XPS and EA. Thus, a highe
oxygen con en in all doped xe ogels compa ed o he e e ence C-XG
sample, induces an inc eased acidi y om 1.8 o a ound 3.0 mmol/g,
slowly inc easing as ollows: C-XG<N-XG<S-XG<O-XG. Simila ly, pH
PZC
alues poin ed ou he mos basic cha ac e o N-XG, which is also
con i med by he highes concen a ion o basic g oups de e mined by HCl
i a ion, i.e., a alue o 5.2 mmol/g.
3.2. Adso p i e beha iou o wa e unde s a ic assays
Conside ing he high RH (90–99 %) used in he s o age came as o
climac e ic ui s, he hyd ophobici y o he adso ben s is one o he
mos de e mining p ope ies. In his con ex , wa e adso p ion was
measu ed g a ime ically o e ime as a i s a emp o es ima e he
in e ac ions be ween he ca bon su ace and he adso ba es. Expe i-
men s we e ca ied ou up o cons an weigh (sa u a ion) in s a ic ai , a
oom empe a u e and 100 % RH. Resul s a e compiled in Table 4 and
Fig. 5. I is well known ha wa e adso p ion is ela ed wi h bo h
mic opo osi y and su ace chemis y, namely wi h he p esence o hy-
d ophilic su ace g oups [51]. Al hough di e en mechanisms o wa e
apo adso p ion we e p oposed, in gene al i is accep ed ha wa e
apo adso p ion is ini ia ed on he su ace unc ional g oups by
hyd ogen bonding. Then, wi h an inc ease in he amoun o wa e
adso bed, hey a e o ming molecula clus e s ha coalesce, a ou ed by
capilla i y occu ed inside he po es, and condense illing he a ailable
po e olume. Thus, he concen a ion and na u e o he su ace g oups
de e mine wa e adso p ion–deso p ion p ocesses.
The in e ac ion o RF ca bon ae ogels wi h wa e was ecen ly
s udied by M´
onika K´
e i e al. [52], who p epa ed wo samples wi h
di e en mic opo osi y (0.35 s. 0.25 cm
3
/g) and mesopo osi y (1.31 s.
0.84 cm
3
/g), bu wi h a simila o al wa e up ake (0.16 cm
3
/g) a 100
% RH, as deduced om wa e adso p ion iso he ms a 25 ◦C. This alue
is signi ican ly smalle han he po e olume deduced by N
2
adso p ion
e en o he leas po ous sample. Addi ional expe imen s ollowed by
nuclea magne ic esonance (NMR) c yopo ome y a e exposing
powde ed samples o di e en amoun s o wa e , de e mined he
amoun o wa e adso bed in each case, which inc eased up o 4.8 and
1.2 cm
3
/g, espec i ely. Resul s showed ha wa e is adso bed on he
hyd ophilic unc ional g oups, o ming wa e clus e s and illing he
mic opo es, acco ding o he mechanism gene ally desc ibed, al hough
he we ing o he mesopo es di e s.
The g owing clus e s o adso bed wa e in mesopo es lead o he
o ma ion o sphe ical wa e d ops which a e non-homogeneously
dis ibu ed. Po e illing is sequen ial and p og essi e, we ing is plug-
like, i.e., only once a po e is illed he we ing passes o he nex po e
h ough he in e connec ed po e s uc u e, inc easing he amoun o
wa e adso bed up o he comple e po e illing a sa u a ion. The
Fig. 4. XPS spec a and decon olu ion o he (a, b) C1s, (c- ) O1s, (g) S2p and (h) N1s egions o selec ed ca bon xe ogels.
Table 3
Quan i ica ion o acidic and basic unc ional g oups in he ca bon xe ogels wi h
Boehm i a ion.
Concen a ion o unc ional g oups (mmol/
g)
C-
XG
O-
XG
S-
XG
N-
XG
Basic su ace g oups 2.5 2.2 2.7 5.2
Ca boxylic g oups 0.4 0.6 0.8 0.5
Lac ones 0.1 0.5 0.2 0.6
Phenols 1.3 1.9 1.8 1.6
To al acidic su ace g oups 1.8 3.0 2.8 2.7
Table 4
Amoun o wa e adso bed by he ca bon xe ogels in s a ic condi ions.
Wa e adso bed C-XG O-XG S-XG N-XG
Q, g (wa e )/ g (sample) 0.473 0.267 0.160 0.389
mg (wa e )/S
BET
0.862 0.545 0.360 1.535
L.T. P´
e ez-Poya os e al.
Jou nal o Colloid And In e ace Science 678 (2025) 480–493
486
mechanism o wa e di usion depends on he deg ee o we ing. When
ini ially wa e o ms clus e s a ound he hyd ophilic unc ional g oups
in he emp y meso- and mac opo es, o e en when he mesopo es a e
pa ially illed, he po osi y is s ill su icien o di usion o ake place
mainly in he apou phase. Howe e , he mic opo es a e easily illed
and, in his case, di usion akes place in liquid phase om and in o he
ee mesopo es ha a e connec ed wi h hese mic opo es. The meso-
po es a e hen illed and inally, e en he mac opo es h ough he
in e connec ed po e s uc u e. When illing mac opo osi y, he olume
o wa e adso bed o e passes he po e olume de e mined om he
co esponding N
2
adso p ion–deso p ion iso he ms, because mac o-
po es a e no quan i ied by his echnique.
Compa ing he adso p i e beha iou o hese ca bon xe ogels wi h
hose epo ed by M´
onika K´
e i e al. [52], a wa e adso p ion capaci y
highe han 0.16 cm
3
/g (Table 4, Fig. 5) is obse ed, al hough ou
samples exhibi a lowe po osi y (Table 2). Thus, i can be concluded
ha he in oduc ion o he e oa oms could e ec i ely enhance he hy-
d ophilic cha ac e o su aces. To explo e he ela ionship be ween
ex u al and chemical aspec s, he amoun o adso bed wa e was plo ed
agains he BET su ace a ea o he samples (Fig. 5a). In gene al, wa e
adso p ion inc eased linea ly wi h S
BET
(Fig. 5a), deno ing he p e-
dominan ac o o he ex u al p ope ies. The highes wa e adso p ion
capaci y obse ed in he N-XG sample (Fig. 5a) migh be jus i ied by he
es ablishmen o hyd ogen bonding be ween N-con aining su ace
g oups and wa e molecules, which is also poin ed ou by he highes
wa e adso p ion capaci y no malized pe su ace a ea uni (Table 4).
Ne e heless, his ype o in e ac ions should also be accessible o
oxygena ed su ace g oups, bu despi e he high hyd ophilici y and
con en o hese g oups, he amoun o wa e adso bed pe squa e me e
o O-XG is signi ican ly lowe han o N-XG, and e en lowe han o C-
XG. In ac , he la ges wa e adso p ion akes place in he undoped
sample (Table 4).
The e o e, conside ing hese esul s, he o e all ex u e was consid-
e ed, ins ead o only he su ace a ea alues. When compa ing he ol-
ume o wa e adso bed di ec ly wi h he o al po e olume de e mined
by N
2
adso p ion a P/P
0
=0.95 (Fig. 5b), a lineal ela ionship be ween
bo h pa ame e s is ob ained, he olume o wa e adso bed a sa u a ion
en i ely ma ching he V
T
, al hough wi h alues sligh ly below. As no ed,
he undoped C-XG sample p esen s now an adso bed olume ha ex-
ceeds he V
T
. This ac could be ela ed wi h i s di e en PSD, in
ag eemen wi h he SEM analysis (Fig. 1), which showed a mo e opened
s uc u e be ween he p ima y pa icle ne wo k, p obably o ming a
la ge ne wo k o mac opo es con ibu ing o wa e adso p ion [52]. The
good linea i y o esul s sugges ed ha he o al wa e adso p ion ca-
paci y is independen o su ace chemis y a sa u a ion in s a ic con-
di ions, po osi y being comple ely illed by adso bed wa e , wi h V
T
de e mined by N
2
adso p ion being a good basis o compa ison be ween
di e en samples.
Howe e , i only he adso p ion capaci y a sa u a ion is conside ed,
he e ec o su ace chemis y may be masked. The combina ion o
po osi y and su ace chemis y e ec s on wa e adso p ion is mo e
e iden when analysing he adso p ion kine ic cu es (Fig. 5c and d).
The e is a clea di e ence be ween he samples acco ding o hei po ous
s uc u e, also in ag eemen wi h he gene al wa e adso p ion mecha-
nism [51,52]. When adso ben s a e mainly mic opo ous (O-XG and S-
XG), he sa u a ion is achie ed a e 2 days a oom empe a u e and
100 % RH, while mesopo ous samples (C-XG and N-XG) con inue
adso bing wa e du ing longe ime pe iods. In ac , he sa u a ion o C-
XG akes place a e a ound 45 days (Fig. 5c) bu he sa u a ion ime o
N-XG is sho e (a ound a mon h), despi e i s la ges mesopo e olume.
Thus, once again, he p esence o hyd ophilic N-con aining su ace
g oups and he mesopo ous cha ac e o his sample could a ou a
as e wa e adso p ion a e, sho ening sa u a ion ime compa ed o C-
XG. Ne e heless, when obse ing in de ail he adso p ion kine ic cu es
Fig. 5. Rela ionship be ween wa e adso p ion capaci y and (a) he BET su ace a ea o (b) he o al po e olume, in s a ic condi ions. (c) Adso p ion kine ic cu es a
long imes and (d) de ails o adso p ion du ing he i s s ages in s a ic condi ions.
L.T. P´
e ez-Poya os e al.
Jou nal o Colloid And In e ace Science 678 (2025) 480–493
487
a low adso p ion imes (Fig. 5d), wa e adso p ion o N-XG is appa -
en ly slowe han he o he samples, indica ing a s onge di usion e-
s ic ion o he mic opo osi y, as p e iously discussed on he e olu ion
o he S
mic o
(CO
2
)/S
mic o
(N
2
) a io (Table 2). These esul s (Fig. 5d)
con i m ha he quick wa e adso p ion is s ongly a ou ed by he
combina ion o a high mic opo ous su ace and he highly hyd ophilic
oxygena ed su ace g oups, bo h aspec s enhancing he adso p ion a e
on O-XG.
3.3. Adso p i e beha iou o e hylene unde dynamic assays
The hyd ophilici y o he samples should in luence hei adso p i e
beha iou o e hylene unde dynamic expe imen s. The co esponding
b eak h ough cu es ob ained in ai low (25 cm
3
/min) con aining
100 ppm o C
2
H
4
unde d y o humid (50 % RH) condi ions a e shown
in Fig. 6a and b, espec i ely. The amoun o e hylene adso bed,
ob ained by in eg a ion o he cu es a he b eak h ough and sa u a ion
poin s (C/C
0
=0.02 and 0.90, espec i ely) in bo h d y and humid
condi ions, is collec ed in Table 5. The e hylene adso p ion depends on
bo h su ace chemis y and a mosphe e condi ions (Fig. 6a and b), he
p esence o humidi y and doping clea ly igge ing a nega i e e ec
(cu es shi ed o a lowe ime on s eam). This beha iou is summa ized
in Fig. 6c, in which a simila decay o he adso p ion capaci y by
humidi y (Red.=~0.12 mg/g, Table 5) is ob ained ega dless o he
po osi y o su ace chemis y o he samples, as well as a p og essi e
educ ion by doping e ec in his sense: C-XG>O-XG>S-XG>N-XG.
Simila esul s we e p e iously epo ed o di e en se ies o ca bon
ma e ials in he adso p ion o non-pola VOCs [53]. Doping wi h
Fig. 6. B eak h ough cu es o e hylene adso p ion unde dynamic assays in (a) d y and (b) humid condi ions. (c) In luence o he e oa om-doping in ca bon xe ogels
on X
0.90
. (d) B eak h ough cu es o wa e adso p ion unde dynamic assays. ( , g) Co ela ions be ween X
0.90
and BET o mic opo ous su ace a eas, espec i ely, in
ca bon xe ogels in d y and humid condi ions.
L.T. P´
e ez-Poya os e al.
Jou nal o Colloid And In e ace Science 678 (2025) 480–493
488
