Boosting CO ₂ Photoreduction via Ligand‐Engineered Single‐Atom Cobalt Sites in Covalent Organic Frameworks

Abstract

Abstract The microenvironment of single‐atom active sites plays a pivotal role in determining the activity and selectivity of the CO 2 reduction reaction (CO 2 RR). Herein, we report a highly efficient single‐atom catalyst, Co‐DABT‐COF, featuring Co(II)‐bithiazole N motifs that achieve exceptional CO 2 photoreduction performance (16.4 mmol g −1 h −1 , 96% selectivity) under visible light irradiation in the presence of a photosensitizer and a sacrificial agent. Through isoreticular design maintaining identical Co‐N 2 O 2 primary coordination, Co‐DABT‐COF exhibits 2.8‐fold higher activity than its bipyridine analogue Co‐Bpy‐COF with Co(II)‐bipyridine N motifs (5.8 mmol g −1 h −1 ). Systematic characterization reveals the 2,2′‐bithiazole ligand significantly enhances charge transfer efficiency and reduces the activation energy barrier for *COOH intermediate formation (0.79 eV versus 1.14 eV). Bader charge analysis demonstrates stronger electron donation from Co sites to CO 2 (0.63 e for Co‐DABT‐COF versus 0.58 e for Co‐Bpy‐COF), facilitating CO 2 activation. This work demonstrates a ligand‐engineering strategy for precisely tuning the electronic structure of single‐atom active sites to achieve efficient CO 2 conversion.