Visible‐Light Photocatalytic Hydrogenation of Nitrobenzenes to Anilines Over Ru‐Complex‐Modified TiO 2

Recently, the chemoselective hydrogenation of nitrobenzenes to their corresponding anilines using photocatalysts working under visible light irradiation has attracted attention as an environmentally friendly method. In this study, we focused on a titanium(IV) oxide (TiO 2 )‐based photocatalyst that does not require complicated preparation process and used various ruthenium complexes to visiblize TiO 2 . We characterized these modified TiO 2 photocatalysts using spectroscopy, including UV–vis, FT‐IR, and XPS, and used them to hydrogenate nitrobenzene (NB) to aniline (AN). Of the various ruthenium complexes and TiO 2 samples tested, the combination of N3 dye (bis(isothiocyanato)bis(2,2′‐bipyridyl‐4,4′‐dicarboxylato)ruthenium(II)) and P25 TiO 2 exhibited the greatest activity, with sufficient performance achieved by modifying with only 0.1 wt% N3 dye. This method is not limited to unsubstituted NB; NBs with reducible groups, such as halogens and vinyl groups, can also be converted to corresponding ANs with high yields. The photocatalytic reduction rate can be increased by slight raising the reaction temperature. This study provides a simple strategy to visiblize TiO 2 , hydrogenate NBs to ANs, and accelerate the photocatalytic reaction.