Ammonium oxalate-mediated synergistic engineering of pores and defects in boron nitride granule catalysts for high-efficiency oxidative desulfurization.

Hexagonal boron nitride (hBN) has garnered significant attention for its structural stability and tunability, yet its industrial application remains constrained by difficulties in recovering powder catalysts and insufficient activity in BN granule catalysts. Herein, we report a metal-free oxidative desulfurization catalyst developed by ammonium oxalate (AO) modification of macroscopic BN granules. This strategy synergistically constructs a hierarchical micro/mesoporous architecture with an ultrahigh surface area (1585.01 m2 g-1) and concurrently introduces nitrogen vacancies and lattice oxygen species. These structural modifications exhibit synergistic effects as the interconnected mesoporous network induces a confinement effect, promoting the enrichment and efficient diffusion of reactants (DBT and O2), thereby significantly enhancing mass transfer. Concurrently, the introduced nitrogen defects and lattice oxygen synergized as highly active sites, driving molecular oxygen activation into superoxide radicals (·O2-) and accelerating interfacial electron transfer. The optimized catalyst achieves complete conversion of dibenzothiophene (DBT) within 80 min and exhibits broad applicability to recalcitrant sulfides such as 4-hydroxydimethyl-dibenzothiophene (4-MDBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). It maintained outstanding long-term stability over 37 consecutive reaction cycles, significantly reducing chemical consumption and waste. This study establishes a novel design paradigm for metal-free catalysts through synergistic pore and defect engineering, providing an economically viable and industrially scalable solution for sustainable fuel desulfurization.