Regulation of the D-Band Center Through Ligand Engineering in Silver Cluster-Based MOFs Enhances Acidic CO₂...

Acidic electrochemical CO₂ reduction reaction (eCO₂RR) offers a promising way for achieving high CO₂ utilization efficiency and circumventing carbonate deposition issues. However, it is plagued by a compromised catalytic performance due to the severe hydrogen evolution reaction (HER). Here, two types of silver chalcogenolate cluster-based MOFs were synthesized through ligand engineering by anchoring Ag₁₂ clusters with tri-topic imidazole and pyridyl ligands respectively. The imidazole-based MOF Ag₁₂THIT demonstrated outstanding performance for the electroreduction of CO₂ to CO. In acidic electrolyte of pH ≈ 2, it achieved a Faradaic efficiency (FE) of 98.5% with a commercial current density of 328.0 mA cm^-2 at - 1.6 V versus RHE. Moreover, the CO partial current density (j_CO) reached a maximum of 447.2 mA cm^-2 with a FE_CO of 96.8% at - 1.7 V versus RHE. No obvious degradation was observed during 70 h of continuous operation, and the performance significantly outperformed those of pyridyl-based MOFs Ag₁₂TPEB and Ag₁₂TPMA. Mechanistic studies revealed that the imidazole ligand endows Ag₁₂THIT with enhanced Lewis basicity and superior σ-donating ability, thereby strengthening the ligand field with an upshifted d-band center and reduced energy barriers. This ligand effect facilitates more efficient electron transfer to *COOH intermediates, thus promoting acidic CO₂ to CO conversion.