Photocatalytic reduction of CO2 to CO using nickel(II)-bipyridine complexes with different substituent groups as catalysts

The photocatalytic reduction of carbon dioxide to carbon monoxide with three new Ni(II)-bipyridine complexes, Ni-1([NiCl2(4,4 '-dichloro-2,2 '-bipyridine)2]), Ni-2 ([NiCl2(4,4 '-dibromo-2,2 '-bipyridine)2]), and Ni-3 ([NiCl2(4,4 '-diphenyl-2,2 '-bipyridine)2]), was studied in this work. The catalysts were applied in a mixture of acetonitrile and water, and tris(bipyridine)ruthenium(II) chloride was used as a photosensitizer in the presence of 1-benzyl-1,4-dihydronicotinamide as electron donor. Under visible-light irradiation, Ni-1 showed higher catalytic performance compared to conventional homogenous Ni-bipyridine catalysts, which was reasonably explained by high-resolution mass spectrometry and density functional theory investigations.