Selective adsorption of CO2 in TAMOF-1 for the separation of CO2/CH4 gas mixtures

A icle h ps://doi.o g/10.1038/s41467-025-58426-w
Selec i e adso p ion o CO
2
in TAMOF-1 o
he sepa a ion o CO
2
/CH
4
gas mix u es
San iago Capelo-A ilés
1,2,15
, Mabel de Fez-Feb é
1,2,12,15
,
Sal ado R. G. Bales a
3
, Juanjo Cabezas-Giménez
1,2,13
,
Raiana Tomazini de Oli ei a
1
,I eneI.GalloS ampino
1
, An on Vidal-Fe an
4,5
,
Jesús González-Cobos
1,14
, Vanesa Lillo
1
, Osca Fabelo
6
,
Edua do C. Escude o-Adán
1
, La y R. Fal ello
7
,JoséB.Pa a
8
,
Paolo Rumo i
9
, Gemma Tu nes Palomino
9
, Ca los Palomino Cabello
9
,
S e ano Giancola
10
,SofiaCale o
11
& José Ramón Galán-Masca ós
1,4
TAMOF-1 is a obus , highly po ous me al–o ganic amewo k buil om Cu2+
cen e s linked by a L-his idine de i a i e. Thanks o i s high po osi y and
homochi ali y, TAMOF-1 has shown in e es ing molecula ecogni ion p op-
e ies, being able o esol e acemic mix u es o small o ganic molecules in gas
and liquid phases. Now, we ha e disco e ed ha TAMOF-1 also o e s a com-
pe i i e pe o mance as solid adso ben o CO
2
physiso p ion, o e ing p o-
mising CO
2
adso p ion capaci y ( > 3.8 mmol g–1)andCO
2
/CH
4
Ideal Adso bed
Solu ion Theo y (IAST) selec i i y ( > 40) a ambien condi ions. Mo eo e , he
ma e ial exhibi s a o able adso p ion kine ics unde dynamic condi ions,
demons a ing good s abili y in high-humidi y en i onmen s and minimal
deg ada ion in s ongly acidic media. We ha e iden ified he key in e ac ions
o CO
2
wi hin he TAMOF-1 amewo k by a combina ion o s uc u al (neu on
di ac ion), spec oscopic and heo e ical analyses which conclude a dual-si e
adso p ion mechanism wi h he majo i y o adso bed CO
2
molecules occu-
pying he emp y oids in he TAMOF-1 channels wi hou s ong, di ec ional
sup amolecula in e ac ions. This e y weak dominan binding opens he
possibili y o a low ene gy egene a ion p ocess o con enien CO
2
pu ifica-
ion. These ea u es iden i y TAMOF-1 as a iable solid-s a e adso ben o he
ealiza ion o a o dable biogas upg ading.
The p esence o CO
2
in gas s eams is dele e ious o he en i onmen
as emissions, bu also p oblema ic as an undesi able impu i y in
indus ial eeds ocks and in me hane-based gas mix u es such as
biogas and na u al gas1,2. The o me is a g een eplacemen o he
la e , whe e me hane is ob ained om he anae obic e men a ion
o biological esidues, as a enewable uel3. I s exploi a ion o e s a
unc ional solu ion o he con e sion o biowas e in o usable
enewable ene gy while educing g eenhouse gases. Biogas upg ad-
ing in o biome hane o be used as a uel (high calo ific alue) which
can mee pipeline g ade equi emen s is o g ea en i onmen al,
economic, and echnological in e es 4,5. Howe e , he sepa a ion and
cap u e o he ca bon dioxide ( ypically a ound 50% in biogas) is an
ex emely challenging p ocess as (i) he CH
4
and CO
2
molecules ha e
simila kine ic diame e s making he sepa a ion o mix u e di ficul
by kine ic/size exclusion; (ii) low-p essu e ope a ions a e p e e ed,
close o 1 ba (low d i ing o ce) o a oid high ene gy-consump ion
om comp ession wo k; and iii) i needs e y high e ficiency in CO
2
emo al (≥98%)6,7.
Recei ed: 2 Sep embe 2024
Accep ed: 17 Ma ch 2025
Check o upda es
A ull lis o a filia ions appea s a he end o he pape . e-mail: sgiancola@o ches asci.com;S.Cale o@ ue.nl;j [email protected]
Na u e Communica ions | (2025) 16:3243 1
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Gas-liquid abso p ion in chemical sol en s (aqueous amine
solu ion)8is he mos ma u e echnology o la ge-scale CO
2
cap u e9,10, including o me hane pu ifica ion11. Howe e , his ech-
nology has h ee majo d awbacks: high ene gy equi emen o sol-
en egene a ion, was e managemen (solid sal s and aces o
gaseous compounds due o amine deg ada ion), and a la ge oo p in .
This calls o he de elopmen o al e na i e solu ions based on no el
and cu ing-edge ma e ials. In pa icula , he sepa a ion o CO
2
/CH
4
mix u es di ec ly in he gas phase would be highly desi able. In his
con ex , a p omising p ocess o gas sepa a ion is physiso p ion12,13.
Due o he physical na u e o he in e ac ions in ol ed, his p ocess
ypically demands lowe ene gy consump ion du ing he egene a ion
s ep when compa ed o p ocesses uled by s ong chemical in e ac-
ions such as chemiso p ion in solid o liquid adso ben s. Di e en
echnologies based on physiso p ion a e a ailable, such as p essu e
swing adso p ion (PSA)14,15, acuum swing adso p ion (VSA)16,and
he mal swing adso p ion (TSA)17. These echnologies in ol e a leas
wo consecu i e s eps. Fi s , CO
2
is selec i ely adso bed by he ac i e
componen a high p essu e and/o low empe a u e, and hen he
adso ben is egene a ed by CO
2
deso p iona lowe p essu e/ acuum
(PSA/VSA) o /and a highe empe a u e (TSA).
Se e al ypes o po ous ma e ials ha e been in es iga ed as phy-
siso ben s o CO
2
emo al18. Benchma k zeoli es ypically exhibi
compe i i e sepa a ion pe o mance, cha ac e ized by high adso p-
ion capaci y and equilib ium selec i i y19. Howe e , while ad an a-
geous o CO
2
emo al om d y emission o p ocess s eams, his
selec i i y is o en comp omised in he p esence o wa e . Wa e
molecules p e e en ially coo dina e wi h exposed me al si es, ou -
compe ing CO
2
20. Fu he mo e, hese ma e ials necessi a e high
egene a ion ene gy19,21,22, which consequen ly inc eases he ope a-
ional expendi u e (OPEX) in indus ial plan s s i ing o high CO
2
15,20.
Ca bon-based ma e ials o e he ad an age o low cos and easy
egene a ion, al hough hey a e limi ed by a lowe adso p ion capaci y
and selec i i y. Nowadays, he limi a ions o he adso ben s a e also
limi ing he comme cial use o ca bon cap u e (CC) echnologies jus
o niche applica ions, whe e he e is no al e na i e. Sui able ma e ials
combining high adso p ion capaci y a low/mode a e wo king p es-
su es, able o disc imina e CO
2
agains molecules wi h simila dimen-
sions (e.g., CH
4
and N
2
) wi h high selec i i y, wi h low-ene gy
egene a ion and as adso p ion/deso p ion kine ics would o e
plausible oppo uni ies o ealize CC no only o biogas upg ading bu
also in many addi ional fields. Especially i CC becomes economically
compe i i e wi h cu en CO
2
emission igh s.
Me al-o ganic amewo ks (MOFs) a e c ys alline and po ous
ma e ials23,24 p epa ed by he sel -assembly o me al ions o clus e s
wi h o ganic ligands o linke s o o m e icula s uc u es25,26.Due o
hei excep ional p ope ies27 such as high accessible su ace a eas (up
o 6200 m2g–1)28, ex a high po osi ies (up o 90%)29, unabili y in po e
dimensions and mo phology30, e sa ile unc ionali y31 as well as
he mal and chemical s abili y32, MOFs a e ecognized as p omising
ma e ials o selec i e gas sepa a ions po en ially able o o e come
in insic limi a ions o common adso ben s33–35. E en hough nowa-
days mo e han70000 MOFs ha e been disco e ed, jus a ew o hem
ha e shown p omising ea u es in o adso p ion/deso p ion p o ocols
o as memb ane componen s o CO
2
cap u e23,36. Some o he mos
ema kable candida es include CALF-20, a Zn-based oxala e-b idged
amewo k wi h high pe o mance inCO
2
cap u e om flue gas, andan
ex ao dina y obus ness unde humid condi ions37;o Mg
2
(dobpdc),
a Mg-based e amine- unc ionalized amewo k wi h ex ao dina y
cyclabili y and s abili y du ing CO
2
cap u e om flue gas. Howe e ,
his las ma e ial is cha ac e ized by chemical CO
2
adso p ion and
needs a high ope a ing empe a u e (100°C)38.In hecaseo CO
2
/CH
4
sepa a ions o biogas upg ading, he mos ele an example is MUF-
16 (Co(Haip)
2
, Haip = 5-aminoisoph halic acid)39.ThisMOFisable o
cap u e ca bon dioxide om hyd oca bons wi h excep ional selec i -
i y al hough wi h mode a e CO
2
adso p ion capaci y40.Mo eo e , he
low isos e ic hea o adso p ion allows o an easy egene a ion s ep.
Ano he in e es ing MOF is Qc-5-Cu-sql, a Cu- quinoline-5-ca boxylic
acid sup amolecula ne wo k, also showing excellen CO
2
/CH
4
selec-
i i y ia he molecula sie ing mechanism. Howe e , also in his case
mode a e CO
2
adso p ion capaci y is epo ed41.Mo eo e ,a ho ough
explana ion o he selec i i y o MOFs o adso bCO
2
isusually missing.
Whe eas chemiso p ion is easie o e alua e om s uc u al da a, he
physiso p ion mechanism emains di ficul o assess. In si u expe i-
men s a e e y a e o disc imina e be ween: (i) size-exclusion p inci-
ples, (ii) kine ically con olled p ocesses, o (iii) he modynamically
con olled p ocesses42.
TAMOF-1 is he fi s in a se ies o homochi al MOFs based on
na u al amino acid de i a i es, by ans o ma ion o he α-amino uni
in o a iazole g oup43,44. TAMOF-1 ([Cu(S-TA)
2
].xH
2
O, S–HTA = (S)-3-
(1H-imidazol-5-yl)-2-(4H-1,2,4- iazol-4-yl)-p opanoic acid) is easily
syn hesized a la ge scale om low-cos aw ma e ials jus by eac ion
o a coppe (II) sal wi h L-his idine de i a i e (imidazole-5-ylme hyl)-
(1,2,4– iazol-4-yl)ace a e (L
1
) in wa e . This ma e ial has a 3D ne wo k,
made om 10 Å wide, helicoidal, in e communica ed channels, deco-
a ed wi h mul iple dangling unc ional g oups ca boxyla e, iazole,
and imidazole (Fig. 1) exhibi ing a BET-specific su ace a ea o
980 ± 50 m2g–1and a mic opo e olume o 0.38 cm3g–1.TAMOF-1
exhibi s excep ional wa e s abili y, wi hs anding bo h hyd a ion/
dehyd a ion cycles wi hou s uc u al deg ada ion o po osi y loss44.
Mo eo e , ac i a ion o gas sepa a ion is achie ed unde mild con-
di ions (353–393 K unde a sweep gas flow), p ese ing he MOF
c ys allini y—a a e ea o Cu-based MOFs and su passing he
equi emen s o ypical MOFs and zeoli es45,46.
In p e ious epo s, we disclosed he pe o mance o TAMOF-1 as
a s a iona y phase o he ch oma og aphic sepa a ion o acemic
mix u es o o ganic subs ances hanks o i s po osi y and
homochi ali y47. The la e was u he exploi ed o he kine ic eso-
lu ion o chi al subs a es by ca aly ic coupling. Mo eo e , he cha -
ac e is ic shape and size o i s channels and po es, as well as he Cu
me al cen e , make TAMOF-1 a good candida e o sepa a ing also a
wide a ie y o ola ile o ganic compounds such as benzene−cyclo-
hexane sys em and xylene isome s (posi ional isome s econnec ion).
The sepa a ion o hese molecules has been p o ed in bo h he liquid
and gas phases48. Fu he mo e, TAMOF-1 has been epo ed o be
capable o sepa a ing C
2
H
2
/C
2
H
4
and C
2
H
2
/CO
2
mix u es49.
Fig. 1 | C ys al s uc u e o TAMOF-1. Rep esen a ion o he c ys al s uc u e o
TAMOF-1, showing he ne wo k o open 10 Å-wide channels. Colo code: Cu, deep
blue; O, ed; N, ligh blue; C, black. Hyd ogen a oms omi ed o cla i y.
A icle h ps://doi.o g/10.1038/s41467-025-58426-w
Na u e Communica ions | (2025) 16:3243 2
He e, we epo ha TAMOF-1 is a highly p omising physiso ben
o esol e CO
2
/CH
4
mix u es and, in a b oade con ex , aiming o
cap u e CO
2
. In pa icula , his ma e ial has highly p omising CO
2
adso p ion capaci y and CO
2
/CH
4
selec i i y. Mo eo e , i allows o a
low ene gy (ambien empe a u e) egene a ion. When compa ed wi h
o he a ailable adso ben s, including o he MOFs, he TAMOF-1 pe -
o mance appea s e y p omising also in e ms o ope a ion cos s. We
an icipa e ha his ma e ial may help o b idge he gap be ween
e ec i e adso p ion and a o dable egene a ion. No ewo hy, he
adso p ion/deso p ion pe o mance emains du able o e ime, e en
in he p esence o wa e , wi h only a small educ ion obse ed when
exposed o highly concen a ed H₂S. By combining specificexpe i-
men al (neu on di ac ion and IR spec oscopy) and heo e ical ools
(Mon e Ca lo and molecula dynamics), we ha e ho oughly eluci-
da ed he molecula mechanism o he physiso p ion and anspo
p ope ies o gas molecules wi hin he TAMOF-1 ne wo k a he o igin
o i s p omising pe o mance.
Resul s and discussion
Gas adso p ion
Single gas (CO
2
,CH
4
,andN
2
) adso p ion iso he ms o TAMOF-1
powde up o 10 ba s we e measu ed in he 293–353K empe a u e
ange (Fig. 2a). As a unc ion o empe a u e, all iso he ms main ain
hei cha ac e is ic shapes, wi h gas up ake inc easing as he em-
pe a u e dec eases, ypical o a physiso p ion p ocess. Type I iso-
he ms a e ob ained o CO
2
, wi hou eaching a pla eau (sa u a ion) in
he in es iga ed p essu e ange. Fo example, a 298 K, CO
2
adso p ion
capaci ies o 3.8 and 6.5 mmol g–1a e ob ained a 1 and 10 ba s,
espec i ely. Linea iso he ms a e ob ained o bo h CH
4
and N
2
,wi h
adso p ion capaci y ollowing he o de CO
2
>>CH
4
>N
2
, indica ing
selec i e p e e en ial up ake o ca bon dioxide.
F om he di e en adso p ion models a ailable (See SI), he dual-
si e Langmui -F eundlich model shows he bes fi ing o he CO
2
adso p ion iso he ms(Supplemen a yFigs. 7–11). See, o ins ance, he
compa ison wi h he single-si e Langmui -F eundlich model in he logq
s. logPplo (Supplemen a y Fig 12). This indica es ha a leas wo
di e en adso p ion si es a e esponsible o dominan CO
2
up ake.
Supplemen a y Tables 16, 17 show he iso he m pa ame e s and
eg ession coe ficien s.
The CO
2
/CH
4
selec i i y calcula ed by he ideal adso p ion solu-
ion heo y a e epo ed in Fig. 2c and in he Supplemen a y Table 18.
A 293 K and 1ba ,45.9, 40.9, and 38.30 selec i i y alues a e ob ained
o espec i ely 30:70, 50:50, and 70:30 CO
2
/CH
4
gas mix u es (in he
ypical biogas composi ion ange). In e es ingly, da a indica e ha
TAMOF-1 is capable o sepa a ing CO
2
/CH
4
mix u es o e a wide
empe a u e ange. Fo example, a 1 ba and 353K,TAMOF-1 hasa CO
2
so p ion capaci y and 50:50 CO
2
/CH
4
ideal selec i i y o 1.8 mmol g–1
and 18, espec i ely. Ano he impo an ea u e is he comple e
adso p ion/deso p ion e e sibili y ob ained o all he gases (Fig. 2b)
wi h no hys e esis obse ed. This beha io aligns wi h he physical
na u e o he gas adso p ion phenomena wi hin he TAMOF-1 ne wo k
and unde sco es he s uc u al igidi y o his ma e ial.
The isos e ic en halpy o adso p ion, ΔH
ads
was es ima ed ia an
indi ec app oach om he CO
2
adso p ion iso he ms a he di e en
empe a u es using he Clausius-Clapey on equa ion ( o a de ailed
desc ip ion o he calcula ions, see SI). Supplemen a y Fig. 13 shows
he e olu ion o –ΔH
ads
wi h CO
2
up ake. A high –ΔH
ads
is ound a low
p essu e (ze o co e age, –ΔH0
ads=0
), and hen i apidly dec eases as
CO
2
up ake inc eases, app oaching he bulk-phase sublima ion hea o
CO
2
,26–27 kJ mol–1, a an adso p ion capaci y highe han
2mmolg
–150. This ene gy ange poin s o a physical gas adso p ion
beha io and deno es a he e ogeneous adso p ion p ocess occu ing
a mul iple adso p ion si es wi h di e en su ace ene gies51.
Sahoo e al.42 conduc ed a p elimina y compa ison o mixed gas
phase CO
2
so p ion capaci y and sepa a ion selec i i y o a ious
MOFs using IAST (Fig. 2d). While many s udies epo only single gas
so p ion capaci y (which is ypically highe han he mixed gas capa-
ci y), he e iew ocused on hose ha p o ided mixed gas CO
2
da a.
Among he MOFs examined, MUF-16 and Qc-5-Cu-sql-βdemons a ed
bo hhighCO
2
so p ion capaci y (1.8 and 1.6 mmol g–1, espec i ely)
and high CO
2
/CH
4
sepa a ion selec i i y (6690 and 3300, espec-
i ely). In e es ingly, TAMOF-1 ( his s udy) exhibi ed an e en highe
mixed CO
2
so p ion capaci y (~ 3.1 mmol g–1)wi haccep ablesepa a-
ion selec i i y (> 40). Gi en he lack o es ablished pe o mance
benchma ks o indus ial-scale biogas sepa a ion, i is p ema u e o
defini i ely assess he po en ial o hese MOFs. We ha e also o men-
ion ha IAST pa ame e s a e calcula ed unde idealized equilib ium
condi ions and do no ep esen he ac ual sepa a ion pe o mance o
adso ben s in dynamic condi ions such as hose ob ained om
b eak h ough cu es. Ne e heless, IAST analysis is usually epo ed
and used o compa e he gas sepa a ion pe o mance o adso ben s
aluable insigh s in o he ela i e adso p ion capabili ies o TAMOF-1
wi h espec o o he adso ben s.
B eak h ough measu emen s
In Fig. 2e, we epo me hane/ca bon dioxide b eak h ough cu es
h ough a TAMOF-1 powde bed a 1 ba and 298 K a di e en CO
2
/
CH
4
a ios. Gas sepa a ion pa ame e s ob ained om he b eak-
h ough cu es a e epo ed in Supplemen a y Table 19 (See SI o
de ails). Pu e me hane (≥99.9%) elu es fi s and speedily om he bed.
Regula S-shaped cu es we e ins ead obse ed o CO
2
. E ec i e CO
2
/
CH
4
sepa a ion is achie ed in all cases as CO
2
is delayed. This confi ms
slowe CO
2
di usion h ough he TAMOF-1 bed. By educing CO
2
mola flow, he ela ed cu es shi owa ds highe b eak h ough imes
(B ).B (CO
2
) inc eases om 16.4 o18.7 min g–1when heCO
2
/CH
4
a io
is educed om 50:50 o 25:75. In con as , B (CH
4
) is almos cons an ,
independen o he CH
4
ac ion. The CH
4
concen a ion o e shoo s
i s equilib ium alue (C/C
0
> 1) be o e e u ning o equilib ium (C/
C
0
= 1). This oll-up e ec indica es p e e en ial adso p ion o CO
2
,
which displaces some o he ini ially adso bed CH
4
. The p ecise shape
o his o e shoo depends on he me hane flow a e, concen a ion,
and adso ben p ope ies20. Adso p ion capaci ies o bo h ca bon
dioxide and me hane we e also measu ed.
Ni ogen is a gas ha can be p esen in combina ion wi h CO
2
and
CH
4
in many gas s eams, hus we also e alua ed CO
2
/CH
4
/N
2
sepa a-
ions h ough TAMOF-1 beds. Fo his pu pose, fixed-bed column
expe imen s we e pe o med by a ying he CH
4
/N
2
a io a cons an
CO
2
concen a ion (50%) (Fig. 2 ).
Ca bon dioxide b eak h ough cu es pe ec ly o e lap inde-
penden ly o he CH
4
/N
2
a io. This indica es ha CO
2
di usion
h ough TAMOF-1 is no a ec ed by he ype o o he gas compo-
nen s (CH
4
o N
2
) in he inle gas mix u e. These gases do no a ec
he adso p ion capaci y, which depends di ec ly on he CO
2
con-
cen a ion, in ag eemen wi h iso he ms measu es (Fig. 2a). As a
consequence, CO
2
adso p ion capaci ies (Supplemen a y Table 19)
a e simila (q
b
= 1.7± 0.06 mmol g–1,q
s
= 2.5 mmol g–1,CO
2
= 50%). A
simila CO
2
/CH
4
selec i i y was also obse ed o a bina y CO
2
/CH
4
(S
s
=6) o a CO
2
/CH
4
/N
2
e na y (S
s
= 4) inle gas mix u e wi h he
same CO
2
concen a ion (i.e., 50%). I is impo an o men ion ha
N
2
, when p esen , exi s as he fi s componen and almos immedi-
a ely om he column wi h elu ion ime almos coinciden wi h he
dead ime.
B eak h ough expe imen s a a iable p essu e condi ions we e
also collec ed (Supplemen a y Table 19). By p essu izing he bed, B
shi s o highe imes wi h me hane emaining always he fi s gas o
elu e. Inc easing bed p essu e om 1.2 o 6 ba a a cons an flow
a e, B (CO
2
) inc eases om 34 o 122 min g–1, and B (CH
4
) om < 4.7
o 32 min g–1.CO
2
adso p ion capaci ies inc ease om 0.42 o
1.24 mmol g–1, bu CH
4
adso p ion also inc eases om < 0.06 o
0.33 mmol g–1. This esul s in a dec ease in he CO
2
/CH
4
selec i i y as
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Na u e Communica ions | (2025) 16:3243 3
a unc ion o inc easing p essu e, om > 7 o < 4 be ween 1.2
and 6 ba .
Highe empe a u es accele a e he gas elu ion, and he CO
2
concen a ion p ofiles sensibly shi owa d lowe B and lowe
adso p ion capaci y (Supplemen a y Table 19). This is in ag eemen
wi h he weake adso ben -adso ba e in e ac ions a highe
empe a u es, he as e molecula di usion and he exo he mic
cha ac e o he adso p ion p ocess. A negligible empe a u e e ec
was ins ead obse ed o CH
4
, ha speedily di uses in o he bed and
almos immedia ely exi s om he bed. Sepa a ion e ec i eness
dec eases by inc easing he empe a u e, and a empe a u es simila
o he ac i a ion one (393 K), CO
2
and CH
4
cu es nea ly o e lap. Good
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sepa a ion capabili y (S
b
>0.9)was oundup o353K,indica ing
applicabili y in a wide empe a u e ange.
Regene a ion and s abili y assessmen o TAMOF-1
The egene a ion s ep o a TAMOF-1 bed a e sa u a ion appea s o be
qui e simple, a oiding he need o he mal hea ing. TAMOF-1 can be
comple ely egene a ed a a cons an empe a u e jus by passing
h ough a sweep gas (N
2
). The co esponding CH
4
and CO
2
deso p ion
cu es a e sa u a ion by an N
2
sweep gas s eam we e collec ed o
di e en flow a es, empe a u es, and p essu es (Fig. 3)
CH
4
deso bs as e han CO
2
, as expec ed. The high CO
2
/CH
4
selec i i y in deso p ion allows o he eco e y o a high pu i y CO
2
ac ion, which can be eused as a commodi y. Mo eo e , he egen-
e a ion imes a e ela i ely sho , when compa ed wi h he B imes.
Fig. 2 | Adso p ion and deso p ion p ope ies o TAMOF-1. a Adso p ion/deso-
p ion iso he ms o CO
2
,CH
4
and N
2
in a TAMOF-1 powde sample a 298 K up o
10 ba . bAdso p ion iso he ms o CO
2
wi h a empe a u e ange o 293–353 K up o
10 ba . cIAST selec i i y o di e en CO
2
/CH
4
gas mix u es wi h a ying a ios a
25 °C up o 1 ba . dCO
2
so p ioncapaci y e susCO
2
/CH
4
IASTselec i i y o bina y
50:50 / mix u es a 1ba and 293 K (IAST selec i i y alues> 20), adap ed om
e . 42.eB eak h ough cu es o CO
2
(solid line) and CH
4
(dashed line) o bina y
mix u es wi h di e en CO
2
/CH
4
a ios: 25:75(blue), 50:50( ed), 75:25(g een). CO
2
b eak h ough cu es in di e en inle gas mix u es: 50:50 CO
2
/CH
4
( ed), 50:50
CO
2
/N
2
(cyan), CO
2
/CH
4
/N
2
=50/
2
5/25 (magen a). Measu es in (eand )we e
pe o med wi h 0.7 g o ac i a ed TAMOF-1 powde . TAMOF-1 was ac i a ed unde
acuum (10−1mba ) in bo h column op and bo om sides a 393K o 15h. gCO
2
/
CH
4
(50:50) b eak h ough cu es o ac i a ed TAMOF-1 (7.7 g) a 72% ela i e
humidi y (RH). TAMOF-1 was ac i a ed unde acuum (10-1 mba ) in bo h column
op and bo om sides a 393 K o 15 h. hCO₂/CH₄(50:50) b eak h ough cu es o
ac i a ed TAMOF-1 (0.7 g) unde acid gas condi ions (0.9% H₂S, 2.5% H₂O). TAMOF-
1 was ac i a ed unde N
2
flow (170 mil min–1g
TAMOF
–1) a 393 K o 15 h. All b eak-
h ough expe imen s we e pe o med a 298 K and 1.05ba . See Supplemen a y
Tables 19–21 o de ailed fixed-bed adso p ion pa ame e s.
Fig. 3 | Gas deso p ion dynamics o TAMOF-1. TAMOF-1 deso p ion cu es o CO
2
( ull line) and CH
4
(dashed line) in a N
2
sweep gas flow o egene a e he TAMOF-1
a e CO
2
-CH
4
b eak h ough expe imen s o (a) di e en concen a ions o equi-
molecula CO
2
-CH
4
mix u es, (b) di e en p essu es, (c)di e en flow a es and (d)
di e en empe a u es. In all cases, he p ocesses we e pe o med a cons an
p essu e, empe a u e, and o e all flow a e du ing bo h, he b eak h ough and
deso p ion s eps. TAMOF-1 (0.7 g) was ac i a ed unde N
2
flow (170 mL min–1
g
TAMOF
–1) a 393 K o 15 h.
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The egene a ion ime can be accele a ed by inc easing he ni ogen
flow a e, o educing he p essu e, o inc easing he empe a u e. All
hese da a highligh he po en ial o TAMOF-1 as an adso ben o
p essu e/ acuum/ he mal swing adso p ion p ocesses.
The p esence o humidi y is inhe en in all aw biogas mix u es,
ypically eaching sa u a ion le els unde wa e 20.F om anenginee ing
pe spec i e, and pa icula ly when employing adso ben s unde
acuum condi ions, pa ial emo al o wa e om he inle s eam
becomes c ucial. This necessi y a ises om he po en ial o wa e
condensa ion wi hin he column, leading o obs uc ions ha can
diminish acuum p essu e du ing he deso p ion phase52. Howe e , i
is impo an o acknowledge ha a ce ain deg ee o wa e apo will
in a iably pe sis in he biogas mix u e en e ing he adso ben col-
umn. P e ious in es iga ions ha e demons a ed he s uc u al
obus ness o TAMOF-1 unde humid condi ions, e en in liquid wa e ,
wi h he ma e ial exhibi ing comple e eac i a ion. He e, we e alua e
he compe i i e adso p ion beha io o CO
2
and H
2
O, as well as he
adso ben cyclic s abili y unde dynamic adso p ion condi ions. As
depic ed in Fig. 2g, e en in he p esence o high humidi y (~ 72% RH),
TAMOF-1 e ains i s CO
2
adso p ion capaci y (2.3mmolg−1)wi hjus a
15% educ ion compa ed o he d y inle mix u e. The CO
2
/CH
4
selec i i y is also main ained wi hin he ange o 4–6. Subsequen o
he adso p ion s ep, egene a ion was conduc ed unde acuum a a
empe a u e o 80 °C. The sepa a ion pe o mance o TAMOF-1
emained consis en o e mul iple adso p ion-deso p ion cycles, as
demons a ed by he o e lapping CO
2
and CH
4
b eak h ough cu es
(Supplemen a y Table 20). This s abili y indica es negligible deg ada-
ion o he ma e iala e successi e cycles andnea -comple e eco e y
o wo king capaci y unde he ope a ing condi ions in es iga ed.
Hyd ogen sulfide (H
2
S), a common impu i y ound in aw biogas
(~ 0–100 ppm1), p esen s a significan challenge o biogas upg ading.
H
2
S is a highly co osi e acid gas ha can comp omise he chemical
s abili y o ma e ials used in sepa a ion p ocesses. Fo ins ance, H
2
S
can dis up hecoo dina ion bonds be ween o ganicligands and me al
cen e s in he MOFs, leading o s uc u al deg ada ion53.Toassess he
sepa a ion beha io o MOFs in he p esence o hyd ogen sulfide is
he e o e c ucial o hei e ec i e applica ion in biogas upg ading.
Analysis o TAMOF-1 in humid (2.5 mol% H
2
O) and acidic gas (0.9 mol%
H
2
S) condi ions (Fig. 2h) demons a es i s abili y o sepa a e CO
2
/CH
4
mix u es, e en unde hese condi ions. Howe e , a educ ion o
adso p ion capaci ies (16%) is obse ed be ween he fi s and he
second cycle, while selec i i y emains ela i ely cons an (~ 3–5). We
obse ed a educ ion in he compe i i e adso p ion be ween CO
2
and
CH
4
, wi h negligible co-adso p ion o CH
4
.Weassign hisdi e ence o
he e y high e en ion ime ound o H
2
S(noH
2
S was de ec ed in he
ou le s eam no e en a e he CO
2
equilib ium egime), which
compe es o adso p ion si es. Impo an ly, his analysis was pe -
o med unde accele a ed condi ions, wi h e y high H
2
S concen a-
ion (9000 ppm), almos wo o de o magni ude highe han wha is
usually ound in biogases. These da a, he e o e, demons a e a ela-
i ely high obus ness o he ma e ial also in s ongly acid condi ions.
Howe e ,H
2
S emo alis ecommended p io obiogasupg adingwi h
TAMOF-1 in o de o inc ease ma e ial du abili y.
S uc u e de e mina ion wi h adso bed CO
2
We a emp ed o localize he p e e en ial c ys allog aphic posi ion o
he CO
2
molecules when adso bed in he TAMOF-1 amewo k by X- ay
di ac ion analysis. A single c ys al was dehyd a ed, exposed o a CO
2
s eam, and hen cooled down o 100 K. The analysis o he XRD
s uc u al da a e ealed esidual densi ies in he channels ha we e
compa ible wi h he p esence o CO
2
in he c ys al ma ix. Howe e ,
he poo selec i i y unde X- ay di ac ion condi ions be ween oxygen
and ca bon, in addi ion o he possible p esence o esidual wa e ,
p ecluded he success ul loca ion o CO
2
molecules in he channels.
Fo his eason, we u ned o neu on di ac ion54, whe e ca bon and
oxygen a oms can be p ope ly iden ified hanks o hei dis inc neu-
on sca e ing leng hs.
The neu on di ac ion s uc u e analysis o an ac i a ed TAMOF-
1 single c ys al confi ms he c ys al s uc u e ob ained by XRD (Fig. 4)
wi h iangula emp y channels unning along he [111] di ec ion, which
is a 3- old axis due o i s cubic symme y (Supplemen a y Tables 1–7).
A e exposu e o CO
2
, and cooling down o 100 K, hese channels a e
filled wi h CO
2
molecules exhibi ing mode a e diso de (Fig. 4), indi-
ca ing ha weak in e ac ions wi h he TAMOF-1 ne wo k a e dominan
(Supplemen a y Tables 8–15). Adjacen o his channel, h ee coppe
a omssel -assemblein wo o ien a ions ha a e o a edapp oxima ely
45° wi h espec o each o he e e y 13.5 Å along he [111] axis, o ming
equila e al iangles o app oxima ely 6.7 Å. This a angemen c ea es
a na owe channel whe e CO
2
molecules align hemsel es wi h he
oxygen’s lone pai s loca ed be ween he Lewis si es o wo o he
coppe a oms in he iangle. These CO
2
molecules a e he only ones
ha exhibi a clea , di ec ional in e ac ion wi h any o he a ailable
TAMOF-1 si es. We associa e his c ys allog aphic posi ion wi h he
highe isos e ic en halpy o adso p ion ound a low co e age. The es
o he CO
2
molecules a e loca ed along he channels o he s uc u e
wi h appa en ly andom o ien a ions.
The in e molecula in e ac ion be ween CO
2
molecules loca ed in
he channel is consis en wi h London dispe sion o ces in ag eemen
ins ead wi h he lowes isos e ic en halpy o adso p ion app oaching
he bulk-phase sublima ion hea o CO
2
. The oxygen a oms in he CO
2
molecules possess lone pai s ha a e di ec ed owa d he mo e posi-
i ely cha ged ca bon a oms, which a e si ua ed a dis ances anging
be ween 2.6 Å and 3.1Å. Simila ly, he ca boxyla e g oups o he
TAMOFin e ac in hesamewaywi h heCO
2
molecules,as heoxygen
a oms in he ca boxyla e g oups exhibi lone pai s ha a e di ec ed
owa ds heca bona omsin heCO
2
molecule, whicha eposi ioneda
adis anceo 3.1Å.
I is impo an o no e ha hese neu on di ac ion da a we e
ob ained a 100 K. Room empe a u e da a collec ion esul ed in a
diso de ed model, indica ing ha oom empe a u e is enough o
b eak he dominan in e ac ions be ween CO
2
and TAMOF-1.
Spec oscopic analysis
To u he in es iga e he in e ac ions be ween CO
2
and he TAMOF-1
amewo k a oom empe a u e, we collec ed IR spec oscopy da a.
The IR spec a o CO
2
when adso bed on TAMOF-1 (Supplemen a y
Fig. 4) show a band a 2335 cm–1, which, acco ding wi h p e ious
epo s55,56, can be asc ibed o physiso bed CO
2
. The less in ense band a
2324 cm–1has also been obse ed be o e and assigned o a combina ion
band. These esul s sugges ha he e a e no si e-specifics ong
in e ac ions and CO
2
only physically in e ac s wi h he amewo k.
To confi m he alidi y o hese esul s, we also in es iga ed CO
adso p ion o compa ison. Supplemen a y Fig. 4b shows he C-O
s e ching egion o ca bon monoxide adso bed on TAMOF-1. In e -
ac ion o he me al-o ganic amewo k wi h adso bed CO esul ed in
he o ma ion o an IR abso p ion band a 2139 cm–1,which,acco ding
o li e a u e, is assigned o (non-localized) physiso bed ca bon
monoxide57, indica ing ha he me al-o ganic amewo k TAMOF-1
does no p esen accessible coo dina i ely unsa u a ed me al cen e s.
Compu a ional analysis and adso p ion mechanism
We calcula ed he single-componen adso p ion iso he ms o CO
2
,
CH
4
,andN
2
molecules in TAMOF-1 in he 263–333 K, and 1–107Pa
ange. The good ag eemen be ween simula ion and expe imen s
alida es ou models (Fig. 5). Excess adso p ion, ollowing he p o ocol
o Mye s and Monson58, allows compa ison wi h he expe imen . Some
ene gy pa ame e s ela ed o ca bon cap u e we e also calcula ed
om he single-componen iso he ms o CO
2
and N
2
. We es ima e ha
TAMOF-1 exhibi s low pa asi ic ene gy, a olume ic wo king capaci y
o 23.46 kg m–3,andafinal CO
2
mola pu i y o he mix u e o 0.904,
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which a e excellen ea u es o ca bon cap u e. The calcula ed
adso p ion iso he ms we e fi ed o a dual-si e ( o CO
2
) and single si e
( o CH
4
and N
2
) Langmui -F eundlich model using he RUPTURA
so wa e59 (solid lines in Fig. 5). Subsequen ly, we p oceeded o com-
pu e he bina y iso he ms and de e mine he adso p ion selec i i y o
CO
2
:CH
4
and 14 CO
2
:84N
2
mix u es ( ep esen ing he composi ion o
d y pos -combus ion flue gas). The esul ing adso p ion selec i i ies
a e depic ed in Fig. 5d. In all cases, he adso p ion o CO
2
su passes
ha o CH
4
o N
2
, p ima ily due o he s onge in e ac ions be ween
CO
2
molecules and he adso p ion su aces.
Simula ion shows ha a low alues o p essu e (1–500 Pa) he
molecules o ca bon dioxide a e loca ed in he na ow channels
o med by he iad o Cu a oms. The e is a dominan in e ac ion
be ween CO
2
and wo Cu a oms (as shown in Fig. 4anddiscussedin he
SI, neu on di ac ion analysis sec ion), esul ing in high alues o he
hea o adso p ion, 50 kJ mol–1, in ag eemen wi h expe imen al esul s
(Qs  Uhg
DE
+RT whe e Uhg
DE
is he mean in e ac ion ene gy
be ween he CO
2
and he TAMOF-1 a e y low p essu e). Howe e , as
he CO
2
p essu e inc eases, he CO
2
-CO
2
in e ac ions become s ong
enough o displace some o he adso bed CO
2
molecules om hese
ene ge ically a o able binding si es. This can be seen om adial
dis ibu ion unc ions be ween CO
2
-CO
2
and CO
2
-Cu a oms, displayed
in Fig. 6.
Figu e 6a shows ha he in e ac ion ene gy be ween he CO
2
molecule and he adso p ion su ace emains s able a a ound
Fig. 4 | C ys al s uc u e om neu on da a showing he occupa ion o CO
2
molecules in o he channels in TAMOF-1. a De ail o he CO
2
posi ions wi hin he
Cu
3
iangles in hela ges oidspace o TAMOF-1. The dis ances O1C-Cu1(zxy) and
O2C-Cu1 a e 2.7726(1) and 2.7068(1) Å, espec i ely. The iew di ec ion is along
[111]. Cu1, Cu1(zxy) and Cu1(yzx) a e ela ed by a c ys allog aphic h ee- old axis,
whichalso ela es heCO
2
moleculea C1C o woo he s,which a eno shown.C1C/
O1C/O2C and i s wo congene s ha e si e occupancy ac o s o 1/3 as a esul o
diso de abou he symme y axis. Colo code: Cu, deep blue; O, ed; N, ligh blue;
C, g ay; H, whi e. bView along [111] o he TAMOF-1 open amewo k (g een s ick
ep esen a ion) and he posi ions occupied by he gues CO
2
molecules ( ed an
de Waals’ adii ep esen a ion) in he TAMOF-1 channels, wi h he wo componen s
shown oge he (le ) and indi idually ( igh ). View along [100] (c)and iewalong
[111] (d), o pa s o he complex oid s uc u e ha accommoda es he gues CO
2
in TAMOF-1. The oids a e ep esen ed as ligh ed a eas o ex e io su aces and as
shadowed a eas o in e io su aces o he oid bounda ies.
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–45 kJ mol–1up o 3 kPa and p og essi ely dec eases wi h p essu e o
–23 kJ mol–1.Al hough his endisquali a i ely equi alen o CH
4
and
N
2
, he ange o ene gies and p essu es di e s, and he e ec on
adso p ion is neglec ed. Fo example, o CH
4
, he in e ac ion ene gy
a ies om –25 kJ mol–1(low p essu e) o –12 kJ mol–1(high p essu e).
To conclude, he adso p ion selec i i y o CO
2
o e CH
4
o N
2
a
in e media e p essu es (Fig. 5d) is mainly explained by wo causes: he
elec os a ic in e ac ions be ween CO
2
and he squa e plana Cu si es,
and he confinemen o CO
2
inside he TAMOF-1 pocke -cages. The
na ow po es o med by he iad o Cu a oms con ibu e o dec ease
his selec i i y a high p essu es.
The sel -di usi i y coe ficien s (D)o CO
2
and CH
4
we e calcu-
la ed using MD simula ions a a ious empe a u es and adso p ion
loadings (Fig. 7). CO
2
consis en ly exhibi s lowe di usi i y han CH
4
.
A low loading (1 o 4 CO
2
molecules pe uni cell), he molecules o
CO
2
a e confined in adso p ion pocke s o med by he iad Cu a oms,
esul ing in low di usi i y (i.e., D
S
CO2 ~10
–10 ms
–1). As p essu e
inc eases, he molecules o CO
2
di use om he pocke adso p ion
si e o he main channel. This leads o a maximum di usi i y a
~ 3 mol kg–1o adso p ion loading o all empe a u es (e.g., a 333 K,
he sel -di usi i y is app oxima ely D
S
CO2 ~10
–9m·s–1). Beyond his
loading( h eemoleculespe Cu iad), hemoleculeso CO
2
a e
mainly adso bed in he (chi al) channel, p e en ing anspo and
causing a p og essi ely dec easing o di usi i y. In con as o CO
2
, o
CH
4
molecules, sel -di usi i y eaches i s peak a infini e dilu ion o
all empe a u es (see Fig. 7b). The di usion o CH
4
dec eases wi h he
inc easeonadso p ion.Asanexample, o 333K and o 1moleculepe
uni cell, he sel -di usi i y coe ficien is D
S
CH4 ~6×10
–9ms
–1.
B eak h ough cu es o CO
2
and CH
4
we e compu a ionally
p edic ed o alida e he expe imen s in a column bed leng h o
5.8 cm and a gas p essu e o 1.05–1.3 ba a 298 K (Fig. 8). The fi ed
Langmui -F eundlich pa ame e s we e used o p edic his adso p-
ion dynamic beha io . Helium was used as a ca ie gas o ensu e
high gas eloci y. Th ee dis inc gas composi ions we e in es iga ed:
95% He and 5% o a CO₂/CH₄mix u e wi h a ios o 1.5:3.5, 2.5:2.5, and
3.5:1.5 ( / ). Ini ially, he column was ully sa u a ed wi h helium. The
oid ac ion o he adso ben bed was 0.3. Simula ion da a a e in
ag eemen wi h he expe imen al esul s (Fig. 8). The simula ed
elu ion gas beha io emains quali a i ely and quan i a i ely con-
sis en wi h expe imen al da a ac oss he ange o gas mix u e
composi ions in es iga ed (3.75%, 2.5%, and 1.25% / CH
4
). Al hough
a di ec compa ison wi h da a epo ed in Fig. 2is no accu a e, he
apid elu ion o CH
4
obse ed in his case may be a ibu ed o i s
highe di usi i y a highe gas eloci y (0.015 m s−1) and o i s low gas
pa ial p essu e (Fig. 7b).
In conclusion, TAMOF-1, a s able, obus , homochi al me al-
o ganic amewo k (BET specificsu acea ea=980±50m
2g–1), has
shown selec i e adso p ion o CO
2
om CO
2
/CH
4
gass eams, o e ing
a p omising pe o mance. Al hough compa ing b eak h ough da a
ac oss s udies is o en challenging due o inconsis encies in expe i-
men al de ails, he pe o mance pa ame e s exhibi ed by TAMOF-1
appea compe i i e o CO
2
/CH
4
sepa a ions when compa ed wi h
s a e-o - he-a (Fig. 2d and Supplemen a y Table 22). As demon-
s a ed by s uc u al and heo e ical da a, CO
2
up ake is domina ed by
a a ie y o weak in e ac ions. A low co e age, he p e e ed binding
si es a e he squa e plana Cu2+ cen e s. Once hese posi ions a e ull,
he TAMOF-1 open channels accommoda e addi ional CO
2
molecules
wi h weake in e ac ions wi h he dangling unc ional g oups (ca -
boxyla e, iazole, imidazole) in he amewo k. Adso p ion iso he ms
confi m heCO
2
p e e en ialup akewi h espec oCH
4
o N
2
in a la ge
p essu e ange, esul ing in good sepa a ion pa ame e s o CO
2
/CH
4
gas mix u es. CO
2
/CH
4
mix u es can be e ec i ely sepa a ed wi h high
selec i i y in a wide CO
2
/CH
4
concen a ion (1–75%), p essu e
(1–6 ba ), and empe a u e ange (293–353 K). Elu ion beha io o CO
2
h ough he TAMOF-1 bed depends jus on he CO
2
mola flow and i is
no a ec ed by he p esence o he o he gases in es iga ed (CH
4
and/
o N
2
).
TAMOF-1 e ains sepa a ion pe o mance, e en unde high humid
condi ions (~72% RH) showing no deg ada ion and high cycling s a-
bili y. Sepa a ion capabili y is obse ed also in ex emely acidic con-
di ions (9000 ppm H
2
S) al hough a small pe o mance deg ada ion is
obse ed. These da a demons a e TAMOF-1 obus ness, also in ha sh
acidic en i onmen s al hough H
2
S emo al is p e e ed o inc ease
ma e ial du abili y.
Fig. 5 | Compu a ional modeling o gas-TAMOF-1 he modynamic p ope ies.
a–cCalcula ed excess adso p ion iso he m (emp y ci cles) and expe imen al iso-
he ms (solid poin s, see legend o mo e de ails) a 263.15, 303.15, 313, 323, and
333 K. E o s a e es ima ed om he s anda d de ia ion in he adso p ion p o-
cesses. d,Selec i i ysi
j=qi=qj,whe eiis CO
2
,andjis CH
4
o N
2
.
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Na u e Communica ions | (2025) 16:3243 8
These p ope ies a e c ucial o indus ial-scale CO
2
cap u e
applica ions. TheweakCO
2
–TAMOF-1 in e ac ions acili a e acile, low-
ene gy egene a ion o he adso ben bed. These a ibu es, coupled
wi h high selec i i y, ende TAMOF-1’spe o manceinbiogas
upg ading supe io o o he epo ed ma e ials42. Consequen ly,
TAMOF-1 appea s well-sui ed o in eg a ion in o p essu e/ acuum/
he mal swing adso p ion p ocesses. A con enien egene a ion p o-
ocol, adap able o specific ime and ene gy cons ain s h ough
ope a ionalpa ame e uning, is eadily achie able. Cu en e o s a e
ocused on scaling and pelle iza ion o TAMOF-1, ad ancing he
de elopmen o a CO
2
cap u e and pu ifica ion echnology based on
his p omising ma e ial.
Me hods
Ma e ials
All eagen s we e o comme cial g ade and used wi hou u he pu -
ifica ion: L-his idine (≥98%, I is Bio ech GmbH), hionyl chlo ide
(SOCl
2
,≥99%, Sigma Ald ich), hyd azine monohyd a e (NH
2
NH
2
·H
2
O,
eagen g ade, 98%, Sigma Ald ich), sodium ca bona e anhyd ous
(Na
2
CO
3
, ACS eagen , ≥99.5%, Sigma Ald ich). All sol en s we e o
comme cial g ade and used wi hou u he pu ifica ion: HPLC-g ade
e hanol, isop opanol, hexanes, ace oni ile and e -bu yl me hyl e he
(VWR, Chem-Lab and Sigma Ald ich), N,N-dime hyl o mamide (pep-
ide g ade, ≥99.9%, I is Bio ech GMBH) and die hyl e he
(≥99%, VWR).
Fig. 6 | Compu a ional modeling o CO
2
-TAMOF-1 in e ac ions. a His og am o he CO
2
-TAMOF-1 in e ac ion ene gy a se e al alues o p essu e. bRadial dis ibu ion
unc ion o (in e molecula ) pai s, and a oms.
Fig. 7 | Gas di usion p ope ies modeling. Sel -di usi i y coe ficien (D) o CO
2
(a)andCH
4
(b) a a ious empe a u es and adso p ion loadings. Solid lines a e fi ed o
he da a as guiding e e ences o assis he eade (u.c.= uni cell).
Fig. 8 | Expe imen al and compu a ional b eak h ough analysis. Calcula ed
(lines) and expe imen al (squa e) b eak h oughcu es o CO
2
andCH
4
a 1 ba and
298.15 K o h ee composi ion a ios: 25 CO
2
:75CH
4
(a),50 CO
2
:50CH
4
(b), and 75
CO
2
:25CH
4
(c). Expe imen s pe o med wi h helium as he ca ie gas (95% / ).
Expe imen s pe o med using 7.7 g o ac i a ed TAMOF-1. TAMOF-1 was ac i a ed
unde acuum (10−1mba ) in bo h column op and bo om sides a 393 K o 15 h.
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