Enhancement of CO2 reduction activity under visible light irradiation over Zn-based metal sulfides by combination with Ru-complex catalysts

Hybrid photocatalysts composed of metal sulfide semiconductors combined with various Ru-complex catalysts were synthesized for use during visible light-driven CO2 reduction with powder suspension systems. A variety of Zn-based sulfides, including Ni-doped ZnS, (CuGa)(0.8)Zn0.4S2 and (AgIn)(0.22)Zn1.56S2, were adopted by conducting the CO2 reduction reaction in acetonitrile containing an electron donor. The photocatalytic activities were found to be largely dependent on the basic characteristics of the Ru-complex and the metal sulfide. The results demonstrate that several of these sulfide semiconductors improve the CO2 reduction selectivity when employed in the semiconductor/metal-complex system, and that (AgIn)(0.22)Zn1.56S2 or Ni (0.2 mol%)-doped ZnS combined with a neutral Ru-complex incorporating a phosphonate ligand [Ru(4,4'-diphosphonate-2,2'-bipyridine) (CO)(2)Cl-2 exhibit the highest CO2 photoconversion activity when synthesizing formic acid, with a turnover number above 100, which catalysts were:stable for 16 h irradiation. These results suggest that metal sulfides are potential candidates for use in powdered semiconductor/metal-complex systems for selective CO2 photoreduction.