Redox-Mediated Ligand Exfoliation Enables High-Density Single-Site Molecular Catalysts for CO2 Electroreduction.

Conventional strategies for fabricating single-site electrocatalysts often suffer from metal aggregation and insufficient exposure of active sites, limiting their efficiency in CO2 electroreduction. Here we present a redox-mediated ligand exfoliation method to construct single-site molecular catalysts with high-density, atomically dispersed active sites in a conductive polymer network. Through tailored integration of molecular assemblies and subsequent reductive cleavage of axially coordinated ligands, coordinatively unsaturated metal sites are exposed on the electrode surface. This architecture enhances CO2 adsorption and activation, facilitating synergistic CO2-to-CO conversion at cobalt sites and subsequent CO-to-methanol transformation at adjacent copper sites. The optimized catalyst achieves a methanol production rate of 9.2 mol h-1 g-1 with partial current density of 142 mA cm-2. In situ spectroscopic and theoretical analyses elucidate the critical role of site exposure in the enhanced activity. This work establishes a generalizable pathway to address the limitations of traditional single-site catalysts in designing electrocatalysts with enhanced site exposure and stability.