Photochemical hydrogen production based on the HCOOH/CO 2 cycle promoted by a pentanuclear cobalt complex.

The first catalytic cycle for hydrogen production based on the photochemical two-electron reduction of carbon dioxide (CO 2 ) and the dehydrogenation of formic acid at ambient temperature was demonstrated using a pentanuclear cobalt complex (Co5). A series of mechanistic studies were performed to elucidate the mechanism responsible for the promotion of the photocatalytic cycle by Co5.