Noble metal-free V2O5/g-C3N4 composites for selective oxidation of olefins using hydrogen peroxide as an oxidant

Abstract

Vanadium pentoxide modified graphitic carbon nitride (V₂O₅/g-C₃N₄) composites were prepared through a method of wet impregnation and calcination. The obtained samples were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, UV-Vis diffuse reflectance spectroscopy, photoluminescence, electron spin resonance and N₂ adsorption/desorption isotherms. Oxidation of olefins was employed to evaluate the catalytic and photocatalytic activities of the prepared V₂O₅/g-C₃N₄ composites. Different weight ratios (1%, 2%, 3%, 4% and 5%) of V₂O₅ loaded composites were prepared and a 3% loaded composite was found to show optimal catalytic performance for the reaction. This noble metal-free catalyst showed excellent performance in the oxidation of styrene to benzaldehyde with high conversion (98.7%) and selectivity (88.4%) under visible light irradiation. A plausible mechanism was proposed for this oxidation reaction with hydrogen peroxide as an oxidant. Other styrene substrates were also selectively transformed to their corresponding aldehydes with high yields (up to 92%), using such a noble metal-free catalytic system.