期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2022
卷号：119
期号：39
DOI：10.1073/pnas.2211544119
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Significance
Direct air capture (DAC) of CO
2 from the atmosphere is being pursued to aid in mitigating global CO
2 amounts and possibly reaching net negative emissions by 2050. We report that a type of commercialized zeolite, mordenite (MOR)-type zeolite, is a promising adsorbent for DAC because of its high CO
2 capacity, high selectivity, fast kinetics, low isosteric heat of adsorption, and high stability under simulated DAC conditions. We demonstrate that the primary site for CO
2 adsorption in the MOR-type zeolite is located at the side-pocket and that its size (i.e., the confinement effect) is the key to the performance by comparing its adsorption behavior to those obtained from a number of other zeolites with varying pore space sizes.
Engineered systems designed to remove CO
2 from the atmosphere need better adsorbents. Here, we report on zeolite-based adsorbents for the capture of low-concentration CO
2. Synthetic zeolites with the mordenite (MOR)-type framework topology physisorb CO
2 from low concentrations with fast kinetics, low heat of adsorption, and high capacity. The MOR-type zeolites can have a CO
2 capacity of up to 1.15 and 1.05 mmol/g for adsorption from 400 ppm CO
2 at 30 °C, measured by volumetric and gravimetric methods, respectively. A structure–performance study demonstrates that Na
+ cations in the O33 site located in the side-pocket of the MOR-type framework, that is accessed through a ring of eight tetrahedral atoms (either Si
4+ or Al
3+: eight-membered ring [8MR]), is the primary site for the CO
2 uptake at low concentrations. The presence of N
2 and O
2 shows negligible impact on CO
2 adsorption in MOR-type zeolites, and the capacity increases to ∼2.0 mmol/g at subambient temperatures. By using a series of zeolites with variable topologies, we found the size of the confining pore space to be important for the adsorption of trace CO
2. The results obtained here show that the MOR-type zeolites have a number of desirable features for the capture of CO
2 at low concentrations.
关键词：enphysisorbentscarbon capturedirect air captureadsorption sitespore space size
