Oxygen Defect Engineering of Hexagonal Perovskite Oxides to Boost Catalytic Performance for Aerobic Oxidation of Sulfides to Sulfones

Abstract Oxygen defect engineering in metal oxides is a promising approach to designing efficient active sites for catalytic oxidation involving surface lattice oxygen. In the present study, a combined approach focusing on the structure of oxygen sites (face‐shared vs corner‐shared) and B‐site substitution in an ABO₃ hexagonal perovskite oxide is investigated. Ru‐substituted SrMnO₃ nanoparticles (SrMn_1−xRu_xO₃) efficiently catalyzes the aerobic oxidation of thioanisole to sulfone with high selectivity (>99%) even at 30 °C, which is much lower than the temperatures required for the same reaction catalyzed using previously reported Mn‐ and Ru‐based oxide catalysts (80–150 °C). Only a small amount of Ru incorporation (x = 0.01) substantially enhances its catalytic performance. The present catalyst can be reused five times and applied to the aerobic oxidation of various sulfides to afford the corresponding sulfones. Mechanistic studies reveal a bifunctional property of SrMn_1−xRu_xO₃, where surface lattice oxygen is involved in sulfide oxidation, and the strong adsorption of sulfoxides onto the surfaces contributes to the rapid successive oxidation of sulfoxide. Catalyst reducibility estimations and density functional theory calculations indicate that the intrinsic role of Ru is likely to enhance the oxygen transferability of face‐shared Mn⁴⁺–O–Mn⁴⁺ species.