Ce-doped MIL-125-NH2 coupled Ce4+/Ce3+ and Ti4+/Ti3+ redox mediators for thermo-enhanced photocatalytic oxidative desulfurization

Photocatalytic oxidative desulfurization (PODS) over efficient earth-abundant catalysts to obtain clean fuel oil is of great importance for the environmental protection. In this work, a series of Ce-doped MIL-125-NH2 photocatalysts were successfully prepared via a simple in-situ doping method and exhibited superior PODS performance of dibenzothiophene (DBT) under mild reaction conditions. The 1.0 mol% Ce/MIL-125-NH2 catalyst achieved 100% sulfur removal within 22 min at 30 °C under visible light illumination, which is mainly attributed to the high surface area and the formation of Ce-Ti-oxo clusters due to electronic coupling. The valence transformation of Ce4+/Ce3+ and Ti4+/Ti3+ redox mediators could not only expose abundant Lewis acid sites, but also promote the separation and transfer of photogenerated charges. In addition, increasing the reaction temperature has been demonstrated to be effective in promoting the PODS performance. Additionally, a thermo-enhanced PODS mechanism was proposed over Ce/MIL-125-NH2, demonstrating the great potential of thermal energy to promote the desulfurization activity.