LAUSR

Abstract Density functional theory (DFT) calculations were conducted to investigate the cobalt porphyrin‐catalyzed electro‐reduction of CO2 to CO in an aqueous solution. The results suggest that CoII−porphyrin (CoII−L) undertakes a ligand‐based reduction to generate the active species CoII−L⋅−, where the CoII center antiferromagnetically interacts with the ligand radical anion. CoII−L⋅− then performs a nucleophilic attack on CO2, followed by protonation and a reduction to give CoII−L−COOH. An intermolecular proton transfer leads to the heterolytic cleavage of the C−O bond, producing intermediate CoII−L−CO. Subsequently, CO is released from CoII−L−CO, and CoII−L is regenerated to catalyze the next cycle. The rate‐determining step of this CO2RR is the nucleophilic attack on CO2 by CoII−L⋅−, with a total barrier of 20.7 kcal mol−1. The competing hydrogen evolution reaction is associated with a higher total barrier. A computational investigation regarding the substituent effects of the catalyst indicates that the CoPor−R3 complex is likely to display the highest activity and selectivity as a molecular catalyst.