Inorganic–organic hybrid polyoxovanadates based on [V₄O₁₂]⁴⁻ or [VO₃]₂²⁻ clusters: controllable synthesis, crystal structures and catalytic properties in selective oxidation of sulfides

Abstract

By rationally controlling hydrothermal conditions, three new inorganic-organic hybrid polyoxovanadates (POVs) [Ni₂(1-vIM)₇H₂O][V₄O₁₂]·H₂O (1), [Cu₂(1-vIM)₈][V₄O₁₂]·H₂O (2) and [Co(1-vIM)H₂O][VO₃]₂ (3) (1-vIM = 1-vinylimidazole) have been synthesized and thoroughly characterized by single X-ray diffraction (SXRD), powder X-ray diffraction (PXRD), infrared spectroscopy (FT-IR), and elemental analyses (EA). Interestingly, complexes 1 and 2 have similar structures including [V₄O₁₂]^4- clusters; complex 3, however, was isolated as a structure by including the [VO₃]₂^2- cluster under a different synthetic condition compared with those of 1 and 2. Both complexes 1 and 2 display an interesting 3D supramolecular structure, and complex 3 shows a 2D two parallel networks supramolecular structure linked by a [Co₂O₂] unit due to the different coordination environments of the central metals. Three inorganic-organic hybrid POVs as heterogeneous catalysts are active in the selective oxidation of sulfides to produce sulfoxides or sulfones with high conversion and high selectivity (up to 99.5% for sulfoxides and 98.5% for sulfones respectively catalyzed by 1). Complex 1 is also used as catalyst in the oxidative CEES (2-chloroethyl ethyl sulfide, a sulfur mustard simulant) abatement with high activity and selectivity toward the corresponding sulfoxide. Moreover, complex 1 can be reused at least three times in sulfoxidation reactions without losing its activity.