Unveiling the mechanism of the electroreduction of CO2 to CO over ZIF-8, ZIF-67, and ZIF-90: a DFT perspective.

The carbon dioxide reduction reaction (CO2RR) is an important solution for reducing carbon levels. Achieving high selectivity and low cost for the catalyst are the main challenges. In this study, computational approaches at the density functional theory (DFT) level are employed to investigate the catalytic activity and mechanism of the conversion of CO2 to CO by zeolitic imidazolate framework (ZIF)-based catalysts (ZIF-8, ZIF-67, ZIF-90). Analysis of the activation energy (E a) barrier reveals that ZIF-8 is the most efficient (E a = 0.39 eV) among the considered catalysts. The quantum theory of atoms in molecules (QTAIM) and noncovalent interaction index (NCI) analyses during the activation step of the CO2 molecule reveal the partial covalent and strong electrostatic interactions between the analyte (CO2 molecule) and the catalysts (ZIF-8, ZIF-67, and ZIF-90) at various sites. The natural bonding orbitals (NBO) and electron density difference (EDD) analyses confirm the charge redistribution and bending of the CO2 molecule as it interacts with the catalyst surface during the activation step. Overall, the study's findings indicate ZIF-8 to be the most stable and effective electrocatalyst surface for the CO2RR.