Tuning of the electronic structure of W=O in h-BN-supported monosubstituted Keggin polyoxotungstate for oxidative desulfurization

Oxidative desulfurization (ODS) is a promising strategy for the removal of sulfur compounds from fuel because of its mild conditions and high selectivity. Furthermore, its efficiency may be notably improved through the precise regulation of the microenvironment surrounding the catalytically active sites. In this work, a series of monosubstituted Keggin polyoxometalates incorporating different transition metals (Fe, Co, Ni) were designed and immobilized on the surface of hexagonal boron nitride (h-BN) using ionic liquids ([C₄mim]BF₄), affording novel supported catalysts for ODS. The Ni-substituted catalyst (PW₁₁Ni-C₄/BN) exhibited high activity and excellent recyclability, which was attributed to the specific electronic structure of the W=O active centers and the strong adsorption capability of the h-BN support. Under optimal conditions (catalyst dosage: 20 mg, O/S ratio: 3, temperature: 60 °C, sulfur content: 500 ppm dibenzothiophene (DBT) in n-octane), sulfur was completely removed within 40 min. In addition, mechanistic studies revealed that hydroxyl radicals (·OH) and superoxide radicals (·O₂⁻) collaboratively drive the catalytic reaction.