Structural transformation of copper-coordinated COFs drives enhanced multi-carbon selectivity in CO2 electroreduction

Covalent organic frameworks (COFs), with their unique structures, have gained attention in CO 2 reduction (CO 2 RR) and are often combined with metal active sites to enhance performance. However, the weak interactions between COFs and metals create ambiguity about their actual states under reaction conditions, hindering the design of high-performance catalysts. Understanding these interactions is therefore essential for the rational development of advanced CO 2 RR electrocatalysts. Herein, a TpBpy COF, synthesized from 2,4,6-triformylphloroglucinol (Tp) and 5,5′-diamino-2,2′-bipyridine (Bpy), was coordinated with copper acetate to serve as a model catalytic system for understanding the structural evolution of TpBpy-Cu during CO 2 RR and the corresponding impact on the catalytic performance. A selectivity shift from CO to multi-carbon products was observed with increasing Cu content and reaction time. By combining ex situ characterization techniques with in situ infrared and Raman spectroscopy, the reduction of TpBpy-Cu to metallic Cu particles was revealed. Density functional theory calculations further demonstrated that metallic Cu surfaces of the resulting Cu particles played a key role in lowering the C-C coupling free energy change, facilitating the production of multi-carbon products. This work provides fundamental insights into the application of copper-based COF composite catalysts in electrocatalytic CO 2 RR and offers valuable guidance for the design of more efficient Cu-COF composite catalysts.