Fabrication of Pd@N-doped porous carbon-TiO2 as a highly efficient catalyst for the selective hydrogenation of phenol to cyclohexanone in water

Abstract

A highly efficient catalyst with the structure of semiconductor–metal heterojunction for phenol hydrogenation in water was fabricated by loading the Pd nanoparticles on the N-doped porous carbon-TiO2 (CN-TiO2) materials, which was synthesized via the one-step carbonization of TiO2-contained ZIF-67. The microstructures of the as-prepared Pd@CN-TiO2 catalysts were investigated in detail and the catalytic properties were tested by the phenol hydrogenation under mild conditions. With increasing TiO2 amount, the charge transfer and specific surface area of Pd@CN-TiO2 initially increase and then reduce, thereby the catalytic performance show a similar regular pattern. The as-fabricated Pd@CN-TiO2 exhibits a superior catalytic performance than the Pd nanoparticles supported on TiO2 or CN separately, owing to their synergistic effect. When the parameters affecting the catalytic efficiency are optimized, the conversion of phenol and selectivity for cyclohexanone can even achieve 98% in pairs with a higher reaction rate of 0.45 mmol h−1. Furthermore, the Pd@CN-TiO2 shows stable performance in the recycling experiments.