A bioinspired molybdenum-copper molecular catalyst for CO electroreduction.

Non-noble metal molecular catalysts mediating the electrocatalytic reduction of carbon dioxide are still scarce. This work reports the electrochemical reduction of CO to formate catalyzed by the bimetallic complex [(bdt)Mo(O)SCuCN] (bdt = benzenedithiolate), a mimic of the active site of the Mo-Cu carbon monoxide dehydrogenase enzyme (CODH2). Infrared spectroelectrochemical (IR-SEC) studies coupled with density functional theory (DFT) computations revealed that the complex is only a pre-catalyst, the active catalyst being generated upon reduction in the presence of CO. We found that the two-electron reduction of [(bdt)Mo(O)SCuCN] triggers the transfer of the oxo moiety to CO forming CO and the complex [(bdt)MoSCuCN] and that a further one-electron reduction is needed to generate the active catalyst. Its protonation yields a reactive MoH hydride intermediate which reacts with CO to produce formate. These findings are particularly relevant to the design of catalysts from metal oxo precursors.