Transferring enzyme features to molecular CO reduction catalysts.

Carbon monoxide dehydrogenases and formate dehydrogenases efficiently catalyze the reduction of CO. In both enzymes, CO activation at the metal active site is assisted by proximate amino acids and Fe-S-clusters. Functional features of the enzyme are mimicked in molecular catalysts by redox-active ligands, acidic and charged groups in the ligand periphery, and binuclear scaffolds. These components have all improved the catalytic performance of synthetic systems. Recent studies impart a deeper understanding of the individual contributions of the various functionalities to reactivity and of their combined effects. New catalyst platforms reveal alternate pathways for CO reduction, unique intermediates, and strategies for switching selectivity. Design of a wider array of complexes that combine different functional elements is encouraged to further optimize catalysts for CO reduction, especially for product formation beyond CO. More diverse bimetallic catalysts are needed to better exploit metal-metal interactions for CO conversion.