Hydrogenation of benzoic acid derivatives over Pt/TiO₂ under mild conditions

Hydrogenation of benzoic acid (BA) to cyclohexanecarboxylic acid (CCA) has important industrial and academic significance, however, the electron deficient aromatic ring and catalyst poisoning by carboxyl groups make BA hydrogenation a challenging transformation. Herein, we report that Pt/TiO₂ is very effective for BA hydrogenation with, to our knowledge, a record TOF of 4490 h^-1 at 80 °C and 50 bar H₂, one order higher than previously reported results. Pt/TiO₂ catalysts with electron-deficient and electron-enriched Pt sites are obtained by modifying the electron transfer direction between Pt and TiO₂. Electron-deficient Pt sites interact with BA more strongly than electron-rich Pt sites, helping the dissociated H of the carboxyl group to participate in BA hydrogenation, thus enhancing its activity. The wide substrate scope, including bi- and tri-benzoic acids, further demonstrates the high efficiency of Pt/TiO₂ for hydrogenation of BA derivatives.