Photocatalytic Reduction of Low Concentration of CO2

A novel molecular photocatalytic system with not only high reduction ability of CO2 but also high capture ability of CO2 has been developed using a Ru(II)–Re(I) dinuclear complex as a photocatalyst. By using this photocatalytic system, CO2 of 10% concentration could be selectively converted to CO with almost same photocatalysis to that under a pure CO2 atmosphere (TONCO > 1000, ΦCO > 0.4). Even 0.5% concentration of CO2 was reduced with 60% initial efficiency of CO formation by using the same system compared to that using pure CO2 (TONCO > 200). The Re(I) catalyst unit in the photocatalyst can efficiently capture CO2, which proceeds CO2 insertion to the Re–O bond, and then reduce the captured CO2 by using an electron supplied from the photochemically reduced Ru photosensitizer unit.