Fabrication of Pd@N-doped porous carbon-TiO ₂ as a highly efficient catalyst for the selective hydrogenation of phenol to cyclohexanone in water

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-TiO ₂ (CN-TiO ₂ ) materials, which was synthesized via the one-step carbonization of TiO ₂ -contained ZIF-67. The microstructures of the as-prepared Pd@CN-TiO ₂ catalysts were investigated in detail and the catalytic properties were tested by the phenol hydrogenation under mild conditions. With increasing TiO ₂ amount, the charge transfer and specific surface area of Pd@CN-TiO ₂ initially increase and then reduce, thereby the catalytic performance show a similar regular pattern. The as-fabricated Pd@CN-TiO ₂ exhibits a superior catalytic performance than the Pd nanoparticles supported on TiO ₂ 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-TiO ₂ shows stable performance in the recycling experiments.