Hydrogen- and noble metal-free conversion of nitro aromatics to amino aromatics having reducible groups over an organically modified TiO2 photocatalyst under visible light irradiation†
A titanium(IV) oxide photocatalyst modified with 2,3-dihydroxynaphthalene (DHN/TiO2) responds to visible light, and electrons are photogenerated to the conduction band of TiO2 under light irradiation in the presence of a suitable hole scavenger. The reducing potential of DHN/TiO2 was applied for photocatalytic conversion of a nitro group to an amino group of aromatics having other reducible groups under hydrogen-free and noble metal-free conditions at room temperature. Various nitro aromatics having vinyl, chloro, bromo, and acetyl groups were converted to amino aromatics with high yields with the reducible groups being preserved. Some parameters affecting the catalytic performance were investigated, and the reaction rate was almost determined by the amount of the substrate adsorbed on DHN/TiO2.