The Facile Construction of Defect-Engineered and Surface-Modified UiO-66 MOFs for Promising Oxidative Desulfurization Performance

The effective and deep removal of unreactive sulfides to achieve ultra-low-sulfur or sulfur-free oils has recently attracted extensive attention. In this work, a series of UiO-66 based catalysts have been prepared facilely for the effective removal of unreactive sulfides. Here, the incorporation of nitro functional groups into UiO-66, along with the construction of defects, results in remarkable sulfur removal for dibenzothiophene (DBT), achieving oil with sulfur content of less than 1 ppm. The successful construction of the designed catalysts was verified through a series of characterization studies. The exposed unsaturated metal sites help provide significantly more active reaction sites. In addition, the incorporated nitro group, with its electron-withdrawing property, would help increase the Lewis acidity of the catalytic metal sites. Thus, the catalytic oxidative capability of the designed UiO-66-based catalysts would be significantly increased. The enhanced catalytic oxidative performance helps ensure acceptable sulfur removal for oils with much higher sulfur concentrations. Additionally, the catalyst developed in this work can also be used to remove the derivatives of DBT with even lower reactivity. The relatively mild reaction conditions, combined with the exceptional sulfur removal, demonstrate the practicality of this reaction system.