Tuning Surface Oxygen Vacancies of Fe-Doped CeVO4 to Promote Direct Hydroxylation of Benzene to Phenol

Catalytic selectivity for producing target products is critical in chemical transformations via heterogeneous catalysis. Herein, the selectivity of direct hydroxylation of benzene to phenol has been evaluated over Fe-doped CeVO₄ catalysts with H₂O₂ as the oxidant. By regulating the feeding ratio of V-to-Ce in a one-pot synthesis approach, we successfully synthesized Fe-CeVO₄ and Fe-CeO₂–CeVO₄ with varying surface vacancies. Under optimal conditions, a phenol yield of 39.1% with a selectivity of 92.5% is achieved over Fe-CeO₂–CeVO₄, which is significantly higher than that observed with Fe-CeVO₄ and physical mixtures of Fe-CeVO₄ and CeO₂. Characterizations, including X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and ammonia temperature-programmed desorption (NH₃-TPD), suggest that the superior catalytic performance of Fe-CeO₂–CeVO₄ arises from the reduction of surface vacancies and the formation of CeO₂ nanoparticles. These factors result in an increase in the Fe²⁺ ratio and weak acid sites, which accelerate hydroxyl radical production to improve benzene conversion and hinder phenol adsorption/overoxidation, thereby promoting phenol selectivity in benzene hydroxylation.