Self-assembly of Dawson-type HPWO@[CuO(TZI)(HO)] for high-performance aerobic oxidation desulfurization of fuel.

Because global sulfur emission has escalated, the development of high-efficiency deep desulfurization techniques has become imperative. Herein, to design a high-activity heterogeneous catalyst for the aerobic oxidation desulfurization (AODS) of fuel, Dawson-type polyoxometalate (HPWO abbreviated as D-PW), characterized by its high activity and strong oxidative capacity, was applied to react with CuCl·2HO and HTZI a one-pot hydrothermal method. Consequently, blue crystalline HPWO[CuO(TZI)(HO)] (abbreviated as D-PW@-MOF-1; -MOF-1 = [CuO(TZI)(HO)]·HO) was afforded. X-ray diffraction analysis indicated that D-PW was successfully encapsulated in two different cages of -MOF-1, which is distinct from the crystal structure of Keggin-type POMs@-MOF-1. It represents the first crystal structure of Dawson-type POMs@-MOF-1. When D-PW@-MOF-1 was employed as a catalyst for AODS under ambient oxygen pressure with the assistance of surfactant dioctadecyl dimethyl ammonium chloride (DODMAC), it demonstrated remarkable catalytic capability and recyclability for both model fuel and commercial diesel. Further, the AODS reaction mechanism, identified as a free radical oxidation-reduction process, was verified by way of radical quenching experiments, EPR and XPS analysis. This approach offers a feasible route for the synthesis of new Dawson-type POMs@MOFs of heterogeneous catalysts for highly active AODS of fuel.