Controllable synthesis, characterization, and catalytic properties of three inorganic-organic hybrid copper vanadates in the highly selective oxidation of sulfides and alcohols

Three novel inorganic-organic hybrid copper vanadates α-[Cu(mIM)₄]V₂O₆ (1), β-[Cu(mIM)₄]V₂O₆ (2), and [Cu(mIM)₂)](VO₃)₂ (3) (mIM = 1-methylimidazole) have been synthesized by rationally controlling of the hydrothermal conditions and fully characterized by single-crystal XRD, powder XRD, elemental analyses, TGA, and FT-IR spectroscopy. Interestingly, compounds 1 and 2 were isolated as geometric isomers by tuning the solvothermal reaction temperature. Because of the different coordination modes between the tetradentate [V₄O₁₂]^4- and [Cu(mIM)₄]²⁺ subunits, the supramolecular structures of the two isomers show a 3D framework with an interpenetrating diamond topology for 1 and a 2D network for 2, respectively. Compound 3 was obtained by tuning the reaction temperature and the ratio of mIM/H₂O, which showed interesting left- and right-handed helixes with an identical pitch of ca. 5.388 Å in its 2D network structure. As heterogeneous catalysts, compounds 1-3 exhibit excellent catalytic performance in the oxidation of sulfides with H₂O₂ as oxidant. Among them, the catalytic activity of 1 (conv. up to 98.7%, sele. up to 100%) outperforms others and can be reused without losing its activity. The activity of 1 is also investigated in the oxidation of various alcohols, and excellent results (conv. up to 98.5%, sele. up to 100%) are obtained.