期刊
CHEMISTRY-A EUROPEAN JOURNAL
卷 20, 期 3, 页码 772-780出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.201303493
关键词
adsorption; carbon dioxide; gas selectivity; microporous materials; polymers
资金
- Korea CCS RD Centre
- IWT through National Research Foundation of Korea (NRF) [NRF-2012-C1AAA001M1A2A2026588]
- Ministry of Science, ICT & Future Planning [2013R1A1A1012998, 2013R1A1A1012282]
- KAIST EEWS Initiative
- NPRP grant from Qatar National Research Fund (a member of Qatar Foundation) [5-499-1-088]
- KUSTAR-KAIST Institute, Korea, under the RD program
- National Research Foundation of Korea [10Z20130011056, 2011-0032170, 2013R1A1A1012282] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
A family of azo-bridged covalent organic polymers (azo-COPs) was synthesized through a catalyst-free direct coupling of aromatic nitro and amine compounds under basic conditions. The azo-COPs formed 3D nanoporous networks and exhibited surface areas up to 729.6m(2)g(-1), with a CO2-uptake capacity as high as 2.55mmolg(-1) at 273K and 1bar. Azo-COPs showed remarkable CO2/N-2 selectivities (95.6-165.2) at 298K and 1bar. Unlike any other porous material, CO2/N-2 selectivities of azo-COPs increase with rising temperature. It was found that azo-COPs show less than expected affinity towards N-2 gas, thus making the framework N-2-phobic, in relative terms. Our theoretical simulations indicate that the origin of this unusual behavior is associated with the larger entropic loss of N-2 gas molecules upon their interaction with azo-groups. The effect of fused aromatic rings on the CO2/N-2 selectivity in azo-COPs is also demonstrated. Increasing the -surface area resulted in an increase in the CO2-philic nature of the framework, thus allowing us to reach a CO2/N-2 selectivity value of 307.7 at 323K and 1bar, which is the highest value reported to date. Hence, it is possible to combine the concepts of CO2-philicity and N-2-phobicity for efficient CO2 capture and separation. Isosteric heats of CO2 adsorption for azo-COPs range from 24.8-32.1kJmol(-1) at ambient pressure. Azo-COPs are stable up to 350 degrees C in air and boiling water for a week. A promising cis/trans isomerization of azo-COPs for switchable porosity is also demonstrated, making way for a gated CO2 uptake.
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