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 (TON_CO > 1000, Φ_CO > 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 (TON_CO > 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.