TiO2 modified with a Ru(ii)–N′NN′ 8-hydroxyquinolyl complex for efficient gaseous photoreduction of CO2

Abstract

A new rigid neutral Ru(II) pincer complex [Ru(N′NN′)(ONO)] was synthesized from cationic [Ru(N′NN′)(MeCN)₂Cl]Cl (N′NN′, 2,6-bis(N-benzyl-benzimidazol-2-yl)pyridine) and 4,8-dihydroxyquiniline-2-carboxylic acid (ONO). The X-ray diffraction analysis indicates that the Ru(II) center adopts a slightly distorted octahedral geometry, in which the two benzyl moieties of the N′NN′ ligand are located on the same side of the coordination plane, defined by three N atoms of N′NN′ and the Ru(II) center, and the dihedral angles of the benzyl group and the Ru(II)–N′NN′ plane are 89.1° and 74.9°, respectively. Upon loading onto TiO₂ nanoparticles (P25), this Ru(II) complex exhibits an efficient CO₂ photoreduction ability with CO/CH₄ production activities of 26.6/17.2 μmol g⁻¹ h⁻¹ in a gaseous photocatalytic system containing CO₂ and H₂O vapor, which is much better than that of the pristine TiO₂ nanoparticles. This result gives a good example of TiO₂ nanoparticles loaded with the Ru(II) pincer complex acting as a heterogeneous photocatalytic CO₂ reduction system, which could facilitate the development of a more feasible artificial photosynthesis system.