A novel molecular photocatalytic system with not only high reduction ability of CO but also high capture ability of CO has been developed using a Ru(II)-Re(I) dinuclear complex as a photocatalyst. By using this photocatalytic system, CO of 10% concentration could be selectively converted to CO with almost same photocatalysis to that under a pure CO atmosphere (TON > 1000, ΦCO > 0.4). Even 0.5% concentration of CO was reduced with 60% initial efficiency of CO formation by using the same system compared to that using pure CO (TON > 200). The Re(I) catalyst unit in the photocatalyst can efficiently capture CO, which proceeds CO insertion to the Re-O bond, and then reduce the captured CO by using an electron supplied from the photochemically reduced Ru photosensitizer unit.

New Ru(ii)–Re(i) diads with bridging ligands constructed of two diimines connected by –CH2OCH2– or –CH2SCH2– were synthesized and investigated as photocatalysts with enhanced oxidation power.