In situ bridging encapsulation of a carboxyl-functionalized phosphotungstic acid ionic liquid in UiO-66: A remarkable catalyst for oxidative desulfurization

Abstract

This work describes a novel approach for linking metal–organic frameworks (MOFs) to polyoxometalates (POMs) for use as effective heterogeneous catalysts in the oxidative desulfurization of fuel oil. A POM-based MOF was synthesized in situ with a carboxyl-functionalized ionic liquid as a bridge to combine the POM and MOF. The resulting [mim(CH2)3COO]3PW@UiO-66 was characterized by XRD, N2 adsorption–desorption, FT-IR, SEM and TGA. The results indicated that the heteropolyanion-based ionic liquid [mim(CH2)3COOH]3PW was successfully dispersed within the cages of UiO-66. The catalyst [mim(CH2)3COO]3PW@UiO-66, which had a high content of the active component and large specific surface area, exhibited remarkable catalytic performance in oxidative desulfurization (100% DBT removal in 60 min). Importantly, a synergistic catalytic mechanism involving W = O and the Lewis acid, in which the Lewis acid promoted the decomposition of H2O2 and the generation of peroxotungstate (W(O2)n), was proposed to explain the high oxidative desulfurization catalytic efficiency of [mim(CH2)3COO]3PW@UiO-66.