Oxidative denitrogenation of liquid fuel over W2N@carbon catalyst derived from a phosphotungstinic acid encapsulated metal–azolate framework

Abstract Tungsten nitride-incorporated carbon (W2N(x)@C) was firstly prepared via pyrolysis of a newly developed phosphotungstic acid-loaded metal-azolate framework-6, PTA(x)@MAF-6 s. The obtained (without ammonia feeding) W2N(x)@C materials, were utilized as catalysts for oxidative denitrogenation (ODN) of fuels. The W2N(x)@C materials, especially W2N(15)@C, under ultrasound (US) irradiation was found to be a very efficient catalyst for oxidative removal of various organo-nitrogen compounds (ONCs). Importantly, the W2N(15)@C showed around 80–147 times turnover frequency those of reported catalysts for stubborn carbazole oxidation. Electron density on the N-atom of the ONCs has a dominant role in the oxidation. The oxidation mechanism was suggested mainly based on the calculated electron density of the reactants and analysis of major intermediates/products. Moreover, the US-assisted ODN was progressed by both non-radical and radical paths, as supported by the electron spin resonance and radical scavenger experiments. The recyclability of the catalyst in the US irradiative ODN was also confirmed.