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Cyclotetrabenzoin Acetate: A Macrocyclic Porous Molecular Crystal for CO2 Separations by Pressure Swing Adsorption

preprint
submitted on 04.02.2021, 14:49 and posted on 05.02.2021, 06:24 by Yao-Ting Wang, Corie M. McHale, Xiqu Wang, Chung-Kai Chang, Yu-Chun Chuang, Watchareeya Kaveevivitchai, Ognjen Miljanic, Teng-Hao Chen
A porous molecular crystal (PMC) assembled by close-packing of macrocyclic cyclotetrabenzoin acetate is an efficient adsorbent for selective CO2 capture. The 7.1´7.1 Å square pore of PMC and its ester C=O group play important roles in improving its affinity for CO2 molecules. Thermodynamically, the benzene walls of macrocycle strongly promote CO2 adsorption via [p···p] interactions at low pressure. In addition, the polar carbonyl groups pointing inward the square channels reduce the size of aperture to a 5.0´5.0 Å square, which offers kinetic selectivity for CO2 capture. The PMC features water tolerance and high structural stability under vacuum and various gas adsorption conditions, which are rare among intrinsically porous organic molecules. In mixed-gas breakthrough experiments, it exhibits efficient CO2/N2 and CO2/CH4 separations under kinetic flow conditions. Most importantly, the moderate adsorbate–adsorbent interaction allows the PMC to be readily regenerated, and therefore applied to pressure swing adsorption (PSA) processes. The eluted N2 and CH4 are obtained with over 99.9% and 99.8% purity, respectively, and the separation performance is stable for 30 cycles. Coupled with its easy synthesis, these properties make cyclotetrabenzoin acetate a promising adsorbent for CO2 separations from flue and natural gases.

Funding

Ministry of Science and Technology of Taiwan (MOST109-2113-M-006-016 to T.-H. C.)

Ministry of Science and Technology of Taiwan (MOST109-2636-E-006-001 to W. K.)

US National Science Foundation (award DMR-1904998 to O. Š. M.)

Welch Foundation (award E-1768 to O. Š. M.)

History

Email Address of Submitting Author

thchen@gs.ncku.edu.tw

Institution

National Cheng Kung University

Country

Taiwan

ORCID For Submitting Author

0000-0001-9879-2162

Declaration of Conflict of Interest

Provisional patent related to this research, entitled "Cyclotetrabenzoin acetate: a macrocyclic porous molecular crystal for CO2 separations by pressure swing adsorption", has been filed by the authors and National Cheng Kung University. US Application No. 63143042, filed on 29 January 2021.

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