Distinct CO₂ Electroreduction Behaviors over Planar and Non-Planar Cobalt Molecular Catalysts

Molecular catalysts serve as ideal platforms for studying electrocatalytic reaction mechanisms. While current research mainly focuses on modulating central metals or surrounding ligands, the influence of molecular spatial configuration remains largely unexplored. Herein, we synthesized two cobalt complexes with similar ligand environments but distinct spatial geometries, a planar cobalt hexaazamacrocyclic complex (CoHAM) and a non-planar acyclic Co(phen)2Cl2, and evaluated their performance in CO2 reduction reaction (CO2RR). The planar CoHAM exhibited dramatically superior CO2RR performance compared to the non-planar Co(phen)2Cl2. Through a series of combined analyses using in-situ UV-vis spectroscopy, high-resolution mass spectrometry (HRMS), and Raman spectroscopy, we elucidated the origins of this performance gap by identifying key intermediates and reaction pathways. These findings underscore the critical role of the spatial configuration of molecular catalysts in governing electrocatalytic performance and provide a strategic direction for the rational design of efficient CO2RR catalysts.