Metal‐Ion‐Coordinated Microenvironments in Covalent Organic Frameworks for Enhanced Photocatalytic CO₂ Reduction

Abstract Metal‐coordinated covalent organic frameworks (M‐COFs) have garnered significant attention for their potential in carbon dioxide (CO₂) photoreduction. However, the efficient conversion of CO₂ to (carbon monoxide) CO remains challenging because of the strong exciton effects from the Coulombic interactions of electron‐hole pairs within the metal‐associated coordination environment. Herein, three benzoxazole (BBO)‐based COF photocatalysts coordinated with cobalt (Co) ions featuring distinct coordination geometries: Co‒N‒O₂, Co‒N‒O₃, and Co‒N₂‒O₂ are strategically designed. The exciton dissociation is precisely modulated and the photocatalytic reduction of CO₂ is enhanced. Among them, BBO‐COF_BPY‐Co demonstrates a significant increase in CO production rate from 5, 024.87 to 10, 552.15 µmol g⁻¹ h⁻¹, and an improvement in the selectivity from 80% to 91%, coupled with excellent stability. Spectral characterizations and density functional theory (DFT) theoretical calculations elucidate that the judicious tuning of the Co atom coordination environment optimized the local electronic structure of the BBO‐COFs which significantly boosts the exciton dissociation, facilitates charge carrier migration within the framework, mitigates the recombination of photogenerated electron‐hole pairs, and reduce the energy barrier of the rate‐determining step. This study provides insight into the pivotal role of metal coordination microenvironments in enhancing the photocatalytic CO₂ reduction process and paving the way for new strategies in exciton regulation within COFs.