Defect engineering of TiO2 for efficient photocatalytic transfer hydrogenation with palladium as cocatalyst and water as a hydrogen source

This is the authors' abstract. We don't add key points for this paper.

Photocatalytic transfer hydrogenation using water as the proton source has emerged as an attractive and green approach for the catalytic reduction of unsaturated bonds. Herein, we report an oxygen-defective TiO 2 -supported palladium catalyst (Pd-TiO 2 -O v ) for efficient photocatalytic water-donating transfer hydrogenation of anethole towards 4-n-propylanisole in a high yield of 99.9%, which is significantly higher compared to the pristine TiO 2 -supported palladium catalyst (Pd-TiO 2 , 74%). The enhanced performance is ascribed to the presence of oxygen vacancies, which facilitate light absorption and suppress the recombination of photogenerated electron-hole pairs. Furthermore, the Pd-TiO 2 -O v is versatile in hydrogenating various alkene substrates including those with hydroxyl, ether, fluoride, and chloride functional groups in full conversion, thus offering a green method for transfer hydrogenation of alkenes. This study provides new insights and advances in current hydrogenation technology with water as the proton source. We report an oxygen-defective TiO 2 -supported palladium catalyst for efficient photocatalytic transfer hydrogenation using water as the proton source, which exhibits high functional group tolerance and broad substrate applicability, enabling the complete conversion of sixteen substrates. • An oxygen-defective TiO 2 -supported palladium catalyst were prepared by H 2 -pretreatment and impregnation for efficient photocatalytic transfer hydrogenation using water as the proton source. • The optimized system exhibited superior catalytic performance for transfer hydrogenation of anethole using water as a proton source with a 99.9% yield of 4-n-propylanisole formation. • The photo(electro)chemical analyses demonstrated that the introduction of the surface defects could enhance light absorption and inhibit carrier recombination. • The reaction mechanism was revealed by isotope-labeling techniques and electron paramagnetic resonance measurements.