Cavity Size Effects on the Adsorption of CO 2 on Pillar[n]arene Structures: A Density Functional Theory Study

• Published in: ChemistrySelect (Weinheim) Vol. 8; no. 29
• Main Authors: Ho, Quoc Duy, Rauls, Eva
• Format: Journal Article
• Language: English
• Published: 04.08.2023
• ISSN: 2365-6549; 2365-6549
• DOI: 10.1002/slct.202302266

Abstract Carbon dioxide (CO 2 ) is the main greenhouse gas that contributes to the global warming. Therefore, CO 2 adsorption is very urgent in the fight to limit global warming below 1.5 degrees Celsius. In this report, the interaction between CO 2 with different structures of pillar[n]arene (P[n]A) is studied by using DFTB and DFT calculations, in order to understand the effect of P[n]A (with n=4, 5, and 6) cavity sizes on CO 2 adsorption. The P[n]A structures physisorb CO 2 at three principally different positions called cavity‐in, top‐in, and top‐out. The adsorbed CO 2 ‐cavity‐in at P[4]A has the highest binding energy. The adsorbed CO 2 at the other positions has similar binding energies on P[4]A, P[5]A, and P[6]A, because hydrogen bonding plays a major role for the interaction at the hydroxyl group. The number of CO 2 molecules that can be adsorbed at the cavity site depends on the cavity size of P[n]A. The bigger the cavity site, the larger the number of CO 2 molecules that can be adsorbed before saturation is achieved. We also observed that the adsorbed CO 2 molecules can interact with each other, leading to an increase of the binding energy and highlighting the promising CO 2 capture capabilities of P[n]A structures.