Covalent Organic Frameworks Boost the Silver-Electrocatalyzed Reduction of CO₂: The Electronic and Confinement Effect

The electrocatalytic reduction of CO₂ to CO with high efficiency is one of the most promising approaches for CO₂ conversion due to its considerable economic feasibility and broad application prospects. In this study, three Ag@COF-R (R = −H, −OCH₃, −OH) hybrids were facilely fabricated by impregnating silver acetate (AgOAc) into respective covalent organic frameworks (COFs) prepared in advance. They differ significantly in the crystallinity, porosity, distribution, size, and electronic configuration of AgOAc species, which thereby influences both the activity and the selectivity of electrolytic CO₂-to-CO transformation. Impressively, Ag@COF-OCH₃ provided a high FE_CO of 93.0% with a high j_CO of 213.9 mA cm^-2 at −0.87 V (vs reversible hydrogen electrode, RHE) in 1 M KOH using a flow cell. In addition, it exhibited long-term durability at 100 mA cm^-2 for 30 h.