An internal electron reservoir enhances catalytic CO2 reduction by a semisynthetic enzyme

The development of an artificial metalloenzyme for CO2 reduction is described. The small-molecule catalyst [Ni-II(cyclam)](2+) has been incorporated within azurin. Selectivity for CO generation over H+ reduction is enhanced within the protein environment, while the azurin active site metal impacts the electrochemical overpotential and photo-catalytic activity. The enhanced catalysis observed for copper azurin suggests an important role for intramolecular electron transfer, analogous to native CO2 reducing enzymes.