Amorphous Cr-doped g-C3N4 as an efficient catalyst for the direct hydroxylation of benzene to phenol

A series of Cr modified graphitic carbon nitride composites (Cr/g-C3N4) was synthesized via a facile wetness impregnation method. Depending on the doping of Cr, the prepared Cr/g-C3N4 catalysts exhibited excellent catalytic performance in the one-step hydroxylation of benzene to phenol with H2O2 as the oxidant under mild conditions. Subsequently, various characterization techniques, including XRD, FT-TR, TEM, XPS, N-2 adsorption-desorption, etc., were used to investigate the physicochemical properties of the prepared materials. The catalyst properties such as crystallinity, the main active Cr species and the surface area have been discussed, providing reasonable correlations for the superior catalyst behavior. With the optimization of the reaction parameters, the catalyst displayed remarkable catalytic ability with the highest phenol yield of 30.9%.