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.