Molybdenum nitride@porous carbon, derived from phosphomolybdic acid loaded metal-azolate framework-6: A highly effective catalyst for oxidative desulfurization

A new composite of the metal-azolate framework (MAF-6) and phosphomolybdic acid (PMA), named PMA(x)@MAF-6, was prepared. Well-dispersed (size: ∼4 nm) Mo₂N, on porous carbon, was prepared without external nitrogen sources firstly via carbonization of the PMA(x)@MAF-6. The prepared catalyst was applied in oxidative desulfurization (ODS) with H₂O₂ as a greenoxidant and showed remarkable performance. A selected catalyst Mo₂N@C-3 had the highest turnover frequency (30 h^-1, around 2–3 times of the best catalyst so far) with the lowest activation energy (27.8 kJ·mol⁻¹) in ODS (with H₂O₂) among any molybdenum-based catalysts. The ODS over Mo₂N@C was explained by a non-radical mechanism via active Mo-peroxo species. Moreover, the high activity of the catalyst is partly because of the contribution of nitrogen in Mo₂N. The studied catalyst could be easily recycled by solvent washing. Therefore, Mo₂N, especially supported on carbon (like Mo₂N@C), could be firstly suggested as a promising catalyst in ODS.