In Situ Ligand-Transformation-Involved Synthesis of Inorganic-Organic Hybrid Polyoxovanadates as Efficient Heterogeneous Catalysts for the Selective Oxidation of Sulfides.

By intentionally involving in situ ligand transformation in the reaction system, two inorganic-organic hybrid polyoxovanadates (POVs), [Co(HDTBA)V2O6] (1) and [Ni(H2O)2(DTBA)2V2O4(OH)2]·4H2O (2), have been synthesized by using a hydrothermal method, where the 3,5-di[1,2,4]triazol-1-ylbenzoic acid (HDTBA) ligand originated from in situ hydrolysis of 3,5-di[1,2,4]triazol-1-ylbenzonitrile in the self-assembly process. The inorganic layers [Co2(V4O12)]n containing [V4O12]4- circle clusters were linked by HDTBA ligands to yield a 3D framework structure of compound 1. There existed a kind of binuclear [(DTBA)2V2O4(OH)2]2- vanadium cluster grafted directly by two DTBA ligands through the sharing of carboxyl oxygen atoms in compound 2, further extended into a 2D layer by nickel centers. The investigations on the catalytic properties indicated that compounds 1 and 2 as heterogeneous catalysts, especially 2, owned satisfying catalytic performances for catalyzing the selective oxidation of sulfides to sulfoxides in the presence of tert-butyl hydroperoxide as an oxidant, accompanied by excellent conversion of 100% and selectivity of above 99%, providing a promising way for developing inorganic-organic hybrid POVs as effective heterogeneous catalysts for catalyzing the selective oxidation of sulfides.