of Fe-MOR(0.25). The small changes in CO 2
uptake and CO 2 /N 2 (CH 4 ) IAST selectivities
during the recycle experiments on CO 2 capture
under saturated humidity (fig. S97) additionally
supported the insignificant water effect on the
gas-sieving capacity of Fe-MOR(0.25), consist-
ent with its low uptake for water vapor (fig.
S98). Compared with the state-of-the-art mois-
ture insensitive adsorbents, such as MOF-based
mmen-Mg 2 (dobpdc) ( 41 )andAl-PMOF( 42 )
(figs. S99 to S106), Fe-MOR(0.25) exhibited
higher volumetric CO 2 uptakes and larger IAST
CO 2 /N 2 (CH 4 ) selectivities. In the breakthrough
experiment, it also showed more rapid N 2 (CH 4 )
breakthrough together with longer CO 2 re-
tentiontimeunderthesameoperationalcon-
ditions when using either dry or humid CO 2 /
N 2 (CH 4 ) mixtures. These comparisons sug-
gest the feasible potential of Fe-MOR(0.25)
for CO 2 capture.
Process simulation
Vacuum pressure swing adsorption (VSA) pro-
cess is an industrial unit operation for sepa-
rating atmospheric gases such as flue gas and
biogas. The separation performance of Fe-
MOR(0.25) was compared with the bench-
marks 13X and Mg-MOF-74 through Aspen
Adsorption simulation of a two-bed VSA pro-
cess (Fig. 4F, figs. S107 to S115, scheme S1, and
tables S10 to S18). Fed with CO 2 /CH 4 (50/50),
Fe-MOR(0.25) showed an energy consumption
of 1.88 MJ Kg(CH 4 )−^1 , recovering 96.9% CH 4
with 94.0 mol% purity while producing high-
purity CO 2 (96.7 mol%) at 94.4% recovery (Fig.
4G and table S17). The overall performance
apparently exceeds 13X and Mg-MOF-74. In
separating CO 2 /N 2 (15/85), Fe-MOR(0.25) out-
performed 13X and Mg-MOF-74 in terms of CO 2
purity (87.2 mol%) when CO 2 recoveries and
energy consumptions were comparable (Fig. 4G
and table S18). The afore-demonstrated mois-
ture resistance of Fe-MOR(0.25) suggests that it
would perform better than 13X and Mg-MOF-74
when real humid gases are supplied as feed.
Summary
Fe-MOR zeolite monolith with ultrahigh me-
chanical strengths was self-assembled in a
binder- and template-free hydrothermal route,
which is cost efficient, energy saving, and envi-
ronmentally benign. A few isolated tetrahedral
Fe species were located inside the 1D micro-
porous channels, leading to a zeolite pore sys-
tem of precisely narrowed microchannels. The
combination of framework Fe species and such
pore characters endowed high CO 2 sorption
capacities, efficient size-based molecular sieving
abilities, and excellent moisture-stable separa-
tion properties. VSA process simulation results
suggest low energy consumption with high
product recovery and purity for this material
in separating CO 2 /N 2 (CH 4 ). All of these fea-
tures render the Fe-MOR monolith a prom-
ising self-molded adsorbent. This work shows
a high-performance self-molded sorbent for
CO 2 capture and highlights the potential of
practical utilization of heteroatom zeolite ma-
terials in gas adsorption and separation.Materials and methods
Fe-MOR(n) series were synthesized using the
acidic co-hydrolysis route. The structure was
characterized by XRD, N 2 (at 77 K), Ar (at 87 K),
and CO 2 (at 195 K) sorption experiments; PALS;
mercury intrusion porosimetry; SEM; high-
resolution HAADF-STEM; x-ray photoelectron
spectroscopy;^29 Si and^27 Al MAS NMR spectros-
copy; ESR spectroscopy; UV-vis spectroscopy;
x-ray fluorescence spectroscopy; thermograv-
imetric analysis; and XAFS. Combined Rietveld
refinements based on high-resolution powder
x-ray and neutron diffraction data were per-
formed using TOPAS-Academic version 6.0.
Single-component gas (CO 2 , Ar, N 2 , and CH 4 )
sorption isotherms were recorded to determine
the gas uptakes, IAST CO 2 /N 2 (CH 4 ) selectiv-
ities, andQst. Kinetic adsorption behavior was
tested on gravimetric analyzers. Experimental
column breakthrough curves were collected to
evaluate the dynamic separation for CO 2 /N 2
(15/85) and CO 2 /CH 4 (50/50) mixtures under
dry and humid conditions. A two-bed VSA pro-
cess simulation was performed using Aspen
Adsorption software. The details of the material
syntheses and the full description of the methods
are available in the supplementary materials.
The supplementary materials and methods
also include optical photographs; SEM and
TEM images; macroporous size distribution
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photoelectron spectroscopy, UV-vis, ESR, and
XAFS spectra; XRD and powder neutron dif-
fraction patterns; combined refinement results;
porosity information; single-component gas
(CO 2 ,Ar,N 2 , and CH 4 ) sorption isotherms;
experimental column breakthrough curves;
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ACKNOWLEDGMENTS
We thank P. Guo and N.-N. Yan (National Engineering Laboratory
for Methanol to Olefins, Dalian National Laboratory for Clean
Energy, Dalian Institute of Chemical Physics, Chinese Academy of
Sciences) for their professional collection of high-resolution
powder XRD patterns for Rietveld refinement; L.-H. He for help on
the powder neutron diffractions for combined Rietveld refinement,
which were performed at GPPD of China Spallation Neutron Source
(CSNS), Dongguan, China (project no. GPPD, P1819061700001);
W.-S. Hung (Chung Yuan University) for PALS analysis; and
Y. Wang, W.-X. Zhuang, and K. Wang (Nanjing Tech University) for
delivery of Mg-MOF-74, preparation of partial controls, and layout
modification of some figures, respectively.Funding:This work
was supported by the National Natural Science Foundation of
China (grants 22072065 and 21136005 to J.W.; grant U1662107 to
Y.Z.; and grants 21938011 and 21725603 to H.X.); the Six Talent
Peaks Project in Jiangsu Province (grant JNHB-035 to Y.Z.);
the Zhejiang Provincial Natural Science Foundation of China (grant
LR20B060001 to X.-L.C.); and the National University of Singapore
Flagship Green Energy Program (grants R-279-000-553-646 and
R-279-000-553-731 to N.Y.).Author contributions:J.W. conceived
the project. N.Y., H.X., and J.W. cosupervised the project. Y.Z. designed
the experiments, analyzed the data, and wrote the manuscript. J.Z.
performed most of the initial experiments. L.W. conducted the
combined Rietveld refinements and solved the structure. X.-L.C.
analyzed all the breakthrough data with conducting partial tests. X.L.
synthesized large amounts of high-quality samples and performed
most of the recent experiments. S.S.W. and H.A. conducted ASPEN
simulation. C.Y. and P.Z. performed humid gas breakthrough tests.
Y.D., S.X., and L.Z. performed the XAFS measurements. X.-Z.C.
conducted the PALS experiment. Y.-X.W. participated in structure
refinement. J.X., Y.-J.W., C.W., H.W., and L.C. participated in partial
experiments. All authors discussed the results and commented on
the manuscript.Competing interests:The authors declare no
competing interests.Data and materials availability:
Crystallography information files (CIFs) of typical samples are
deposited at the Cambridge Crystallographic Data Centre (CCDC,
http://www.ccdc.cam.ac.uk) under reference numbers of 2006395
for Fe-MOR(0) and 2006396 for Fe-MOR(0.25). All other data
needed to evaluate the conclusions in the paper are present in the
main text or the supplementary materials.SUPPLEMENTARY MATERIALS
science.sciencemag.org/content/373/6552/315/suppl/DC1
Materials and Methods
Scheme S1
Supplementary Text
Figs. S1 to S115
Tables S1 to S18
References ( 43 Ð 59 )
19 April 2019; resubmitted 30 May 2020
Accepted 7 June 2021
10.1126/science.aax5776320 16 JULY 2021•VOL 373 ISSUE 6552 sciencemag.org SCIENCE
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