Experimental and Theoretical Study on Mononuclear Nickel Complexes for CO 2 Photoreduction

The photocatalytic CO 2 reduction technology, which utilizes light energy to convert CO 2 into some chemicals, is an important method for achieving sustainable carbon cycling. Herein, a kind of novel nickel-sulfur complexes NqbS 1 and NqbS 2 were successfully synthesized by introducing 2-(2-pyridyl)benzimidazole and 2-(-thiazolyl)-1H-benzimidazole as ligands. NqbS 1 exhibited excellent photocatalytic CO 2 reduction activity. Under optimized conditions, the CO yield of NqbS 1 reached 1310.11 μmol•g -1 using Ru(bpy) 3 Cl 2 as a photosensitizer and ascorbic acid as an electron sacrificial donor. The analysis of high-performance liquid chromatography-mass spectrometer shows the concentration of HCOOH was 68.55 mg/L in the reaction solution. Density functional theory calculations showed the nickel atoms could be active sites and the electron transfer between NqbS 1 and the photosensitizer occured fast, facilitating the reduction of CO 2 around it. Finally, the CO 2 reduction mechanism was discussed by experimental and theoretical methods. This study provides new insights for designing efficient photocatalysts for CO 2 reduction.