Investigations of Functional Groups Effect on CO ₂ Adsorption on Pillar[5]arenes Using Density Functional Theory Calculations

Abstract This study investigates how various functional groups affect the adsorption of carbon dioxide (CO 2 ) in pillar[5]arenes (P[5]A) at the aim of enhancing CO 2 capture in P[5]A for environmental applications. Density functional theory (DFT) and density‐functional‐based tight‐binding (DFTB) methods were employed to investigate the adsorption behavior of CO 2 in pillar[5]arenes (P[5]A) with various functional groups including P[5]A with methyl (P[5]A‐OCH 3 ), aldehyde (P[5]A‐OCOH) functional groups and pillar[5]quinone (P[5]Q). Self‐consistent charge DFTB calculations have been performed using the DFTB+ code, with dispersion corrections included for van der Waals interactions, to ensure accurate results at a lower computational cost. Bader charge analysis have been carried out with VASP code to understand the interaction mechanisms and charge transfer between P[5]A and CO 2 . The study demonstrates that changing the functional groups of P[5]A affects CO 2 adsorption behavior. Specifically, CO 2 adsorption is more favorable at the cavity site of P[5]A‐OCH 3 compared to other functional groups, due to the combined effects of weak hydrogen bonds and π‐π interactions. The calculated results shows that the functionalization is one of the beneficial factors for CO 2 capture in pillararenes, the adsorption energy and configuration of adsorbed CO 2 at P[5]A are affected by both the polarization and geometry of the functional groups. Furthermore, the density of states (DOS) calculations confirm that CO 2 is only physisorbed in P[5]A, ensuring the reusability of pillararenes after desorption. The findings of this study suggest that modifying the functional groups of pillararens is a promising strategy for developing high‐efficiency CO 2 capture materials.