Zr-Based Metal–Organic Framework (UiO-66) Doped with Rare-Earth Element (La, Y)-Supported Polyoxometalate Liquid for Oxidative Desulfurization of Dibenzothiophene Oxidation

By designing metal–organic frameworks (MOFs) doped with rare-earth elements, we can enhance catalytic activity and stability in a novel way. In the realm of oxidative desulfurization (ODS), polyoxometalate-ionic liquids have outstanding desulfurization performance. Herein, to create La-UiO-66 and Y-UiO-66, respectively, rare-earth elements (REs) of yttrium (Y) and lanthanum (La) were doped into the Zr-based metal–organic framework UiO-66. After that, the catalyst [C₁₂mim]₃PW₁₂O₄₀/RE-UiO-66 was prepared by supporting a type of polyoxometalate-ionic liquid [C₁₂mim]₃PW₁₂O₄₀ with a large specific surface area and stable structure on RE-UiO-66 (RE = La or Y). The catalyst was characterized and analyzed by XRD, FT-IR, SEM, and other methods. The ODS reaction of the dibenzothiophene model oil was conducted in the oxidative desulfurization experiment with H₂O₂ as the oxidant and [C₁₂mim]₃PW₁₂O₄₀/RE-UiO-66 as the catalyst, and the ideal reaction conditions were determined. Under the optimum reaction conditions (T = 60 °C, O/S = 5), due to the strength of electron transfer over the catalysts, the DBT removal efficiencies of [C₁₂mim]₃PW₁₂O₄₀/0.18La-UiO-66–25% and [C₁₂mim]₃PW₁₂O₄₀/0.09Y-UiO-66–25% were 100% in 40 min and 97% in 60 min, respectively. The desulfurization efficiency was maintained at 91% after 13 cycles with [C₁₂mim]₃PW₁₂O₄₀/0.18La-UiO-66–25% as a catalyst. In addition, a proposed reaction mechanism for the ODS reaction over this catalyst was presented.