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]₂²⁻ 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.