Room-temperature oxidative desulfurization with tungsten oxide supported on NU-1000 metal–organic framework

A homogeneously dispersed and immobilized tungsten oxide (WO₃) catalyst supported on a metal–organic framework (MOF) NU-1000 was prepared for the first time and applied for the oxidation of organic sulfur compounds (OSCs) from liquid fuels. The composite was prepared at room temperature; therefore, cost-effective and environmentally friendly. The defective sites of NU-1000 helped the firm immobilization of WO₃ species within the NU-1000 pores. The composite material denoted as W@NU-1000 was prepared from ammonium tungstate para pentahydrate in the presence of NU-1000 using nitric acid as a precipitating agent. The material was characterized by several techniques including XRD, FTIR, TGA, N₂ adsorption–desorption, XPS, SEM, and TEM. The material showed remarkable performances in the oxidative conversion of dibenzothiophene (DBT, a typical OSC) using H₂O₂ as an oxidant. For example, almost complete conversion of DBT (1000 ppm) was achieved at room temperature within 120 min of the reaction, and the activation energy was very low of 25.9 kJmol⁻¹. The remarkable performance of the catalyst might be due to the well-dispersed WO₃ (that can effectively activate H₂O₂) and relatively high porosity. The radical scavenger experiments and electron spin resonance analyses confirmed a non-radical pathway for the oxidation of DBT probably by the formation of a W⁶⁺-peroxo complex during the oxidation process. The material W@NU-1000 could be used for five cycles without any loss in performance, suggesting that it can be utilized as a potential oxidation catalyst.