Direct hydroxylation of benzene to phenol by supported vanadium substitution polyoxometalates using H2O2 as oxidant

A practical method for the direct hydroxylation of benzene to phenol catalyzed by supported vanadium-substituted polyoxometalates using H2O2 as an oxidant is described. Three vanadium-doped polyoxometalate Na2H3PMo10V2O40·xH2O catalysts were designed and prepared through support on graphitic carbon nitride (g-C3N4), montmorillonite, and activated carbon and named as CN-PMoV2, M-PMoV2, and C-PMoV2, respectively. Their characterization was elucidated through the Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), inductively coupled plasma-atomic emission spectrometry (ICP-AES) and scanning electron microscopy (SEM). This heterogeneous catalyst demonstrated promising activity in the hydroxylation of benzene to phenol with H2O2. Especially, CN-PMoV2 catalyst was highly active and selective even under mild conditions. Moreover, CN-PMoV2 catalyst still has a certain catalytic effect even after three instances of repeated use.