Amorphous MoaZr0.8Ox-500 catalyzed selective oxidation of sulfides to sulfoxides mediated by 1O2 from direct heterolytic cleavage of H2O2

Abstract

Sulfoxides, a class of pharmaceuticals and fine chemicals of significant importance, are readily peroxidized to sulfones in the H₂O₂ system. Altering the intermediate oxygen species is the key to achieving selectivity regulation. Herein, Zr(OH)₄ was used to support Mo species, after calcining at 500 °C, obtaining a unique amorphous composite oxide with Mo uniformly dispersed in the ZrO₂ matrix (Mo_aZr_0.8O_x-500). Mo_aZr_0.8O_x-500 demonstrates enhanced catalytic proficiency, enabling the synthesis of sulfoxides within 30 minutes at 30 °C. Reactive oxygen species (ROS) quenching experiments and EPR spectra indicate that Mo_aZr_0.8O_x-500 possesses the ability to rapidly and directly participate in the heterolytic cleavage of H₂O₂ to produce ¹O₂ without passing through the intermediate ˙O²⁻, preventing the peroxidation of sulfoxides to sulfones. Additionally, the prevalence of basic sites in Mo_aZr_0.8O_x-500 is conducive to proton transfer, which plays a significant role in the heterolytic cleavage of H₂O₂. Furthermore, Mo_aZr_0.8O_x-500 exhibits excellent reproducibility, scalability, and broad substrate applicability. This study provides new insights into the selective regulation of the sulfide oxidation reaction, as well as the preparation of amorphous solid solution.