Direct catalytic hydroxylation of benzene to phenol catalyzed by vanadia supported on exfoliated graphitic carbon nitride

•G-C3N4 materials treated by exfoliation and protonation procedures.•Simpler and more eco-friendly method than that applied for mesoporous g-C3N4.•Protonation increased the percentage of terminal amino groups.•Vanadia supported on peg-C3N4 showed superior activity to those on pristine g-C3N4.

Direct hydroxylation of benzene is a sustainable and promising strategy to synthesize phenol. The key topic for the catalytic process is the development of an efficient heterogeneous catalyst. In this work, graphitic carbon nitride (g-C3N4) material was exfoliated and protonated, and then utilized as a support to load vanadia by using VO(acac)2 as a precursor. The synthesized materials were characterized by several techniques including N2 adsorption-desorption, XRD, TG, TEM, SEM, FT-IR, UV-vis, and XPS. The results exhibited that the exfoliation as a simple method could improve the surface area and pore volume of g-C3N4, while protonation was able to facilitate to increase the loading amount of vanadia. In hydroxylation of benzene to phenol in the presence of H2O2, the vanadia catalysts supported on peg-C3N4 demonstrated superior catalytic activity to the catalysts supported on the pristine g-C3N4. Moreover, the effects of protonation conditions including acid concentration and temperature on the final catalytic activity have also been investigated. Under optimized conditions, a maximum yield of phenol reached 15% at 60 °C.

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