Bio-inspired benzimidazole-functionalized manganese terpyridine complexes for electrochemical CO₂ reduction

Inspired by the active site of carbon monoxide dehydrogenase (CODH), where a pair of amino acids facilitating hydrogen bonding manages the reversible interconversion of CO and CO₂ with high efficiency, we developed a family of manganese terpyridine derivatives (1-4), in which a benzimidazole moiety functions as a proton relay to assist the CO₂ reduction reaction (CO₂RR). To regulate the position of the proton donor, the benzimidazole moiety was introduced into the framework by two approaches, and the pK _a of the proton relay was adjusted by methylation of the benzimidazole moiety. We found that all such designs led to a sharp corruption in the activity of electrochemical CO₂ reduction compared with that of our previously reported analogues. The corruption was ascribed to the pK _a of the benzimidazole moiety, which resulted in inefficient proton exchange.