Selective Oxidation of Benzyl Alcohol to Benzaldehyde in a Non-aqueous Solution Using a Quaternary Nanocomposite Photocatalyst

Abstract

In this work, functionalized nanostructured quaternary photocatalysts based on graphitic carbon nitride (g-C₃N₄) and graphene oxide (RGO) as a support, with iron oxide (FeNPs) and zinc oxide (ZnO) (g-C₃N₄/FeNPs/RGO/ZnO), were synthesized by a hydrothermal method and used as an efficient visible photocatalyst for the selective oxidation of benzyl alcohol to benzaldehyde using atmospheric oxygen. The g-C₃N₄/FeNPs/RGO/ZnO photocatalyst shows good oxidation activity and selectivity for benzyl alcohol under visible light. The as-synthesized catalyst was thoroughly characterized using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Raman spectroscopy to identify its chemical structure and composition. Various experiments were conducted to fine-tune reaction selectivity, including reactions with the support, with the support doped with iron and zinc oxide, and control experiments using benzaldehyde and without catalysts. The optimized amount of the developed photocatalyst was 10 mg. Various concentrations of benzyl alcohol were studied using the g-C₃N₄/FeNPs/RGO/ZnO photocatalyst, and the conversion and selectivity for benzyl alcohol to benzaldehyde were 65% and 67%, respectively, at room temperature. Interestingly, (i) the reaction proceeds only from benzyl alcohol to benzaldehyde, and (ii) no reaction was observed in the absence of a catalyst and light. The reaction was monitored by liquid chromatography/mass spectrometry. The synergistic effect among the surface Fe NPs, ZnO, and g-C₃N₄ plays a vital role in achieving good photocatalytic performance.