Highly Selective Synthesis of Phenol from Benzene over a Vanadium-Doped Graphitic Carbon Nitride Catalyst

Design and preparation of efficient and economical catalysts for direct hydroxylation of benzene to phenol is an important topic. In this work, a series of metal-doped graphitic carbon nitride catalyst (Cu-, Fe-, V-, Co-, and Ni-g-C3N4) were successfully synthesized by using urea as the precursor through a facile and efficient method. The catalysts were characterized systematically using N-2 adsorption-desorption, FTIR, thermogravimetric analysis, powder X-ray diffraction, and X-ray photoelectron spectroscopy techniques. It was found that the vanadium-doped graphitic carbon nitride catalyst V-g-C3N4 was the most efficient catalyst for the direct synthesis of phenol from benzene with hydrogen peroxide as the oxidant and it could be recycled at least 4 times. The influence of reaction conditions such as the solvent, reaction temperature, reaction time, and the amounts of catalyst and hydrogen peroxide were investigated. Under optimized conditions, 18.2% yield of phenol was obtained with the selectivity to phenol as high as 100%.