Selective oxidation of sulfides catalysed by WO3 supported on chitosan-derived carbon

Abstract

Sulfones are valuable compounds with diverse applications in pharmaceuticals and materials science. In this study, we present a promising approach for the efficient oxidation of sulfides to sulfones using WO₃ supported on chitosan-derived carbon as a heterogeneous catalyst. The method is based on the green synthesis of WO₃ particles via the coprecipitation method, followed by their impregnation onto a carbon support obtained through chitosan pyrolysis, with loadings of 10, 20, and 40% (w/w). The heterostructure of the WO₃/carbon nanocomposite promotes charge separation due to interactions between the semiconductor and the π electrons of the carbon matrix. Among the tested catalysts, the 20% WO₃ composition exhibited the best performance. The optimized reaction conditions were 60 °C, 120 min of reaction time, 8 equivalents of oxidant (H₂O₂), and 10 mg of catalyst. The choice of solvent played a crucial role, with conversions exceeding 99% achieved in both acetonitrile and water. However, catalyst stability was higher in water, while deactivation in acetonitrile was attributed to WO₃ leaching, as confirmed by X-ray photoelectron spectroscopy analysis. Beyond its excellent scalability, the catalytic system effectively oxidized a wide range of substrates, in particular in acetonitrile. Mechanistic investigations revealed that hydroxyl radicals (*OH) and singlet oxygen (¹O₂) were the primary reactive species driving the oxidation process. This work underscores the versatility and robustness of WO₃/carbon catalysts for sulfide oxidation, establishing a promising platform for sustainable and efficient chemical transformations.