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.