Multidimensional all-inorganic frameworks based on new molybdovanadate cluster of [VMo7O28]9− with Cu(ii) linker showing semiconducting behavior

Abstract

Three multi-copper molybdovanadate cluster compounds [Cu₈(OH)₂(H₂O)₂V₁₀Mo₃₀O₁₃₂]²⁰⁻ (1), {[CuNa(H₂O)₆][Cu(H₂O)₄]₂[Cu₈(OH)₂(H₂O)₂V₉Mo₃₀O₁₂₈]}¹⁰⁻ (2), {[Cu_0.5Na_0.5(H₂O)₃][Cu(H₂O)₄]₂ [Cu₆(OH)₂(H₂O)₂V₉Mo₂₃O₁₀₈]}^9.5− (3), containing a novel [VMo₇O₂₈]⁹⁻ fragment, have been isolated by using a one-pot self-assembly method. These three compounds were characterized by elemental analysis, single-crystal X-ray diffraction, IR spectroscopy, UV-vis spectroscopy, cyclic voltammetry, magnetic properties analysis, and thermal gravimetric analysis. The Z-shaped [Cu₈(OH)₂(H₂O)₂V₉Mo₃₀O₁₂₈]¹⁷⁻ anions of compound 2 can transform into the banana-shaped {Cu₆(OH)₂(H₂O)₂V₉Mo₂₃O₁₀₈} units of compound 3 by only changing the pH from 4.5 to 5.0, while the introduction of nitrilotriacetic acid as an assistant ligand ensures the formation of the zero-dimensional compound 1. Magnetic studies indicate the presence of strong antiferromagnetic interactions in compounds 1–3, and the three compounds also exhibit obvious electrocatalytic activities for nitrate reduction. The semiconducting properties of these solid state compounds were revealed from the measurements of the diffuse reflectance UV-vis spectra, in which the band gap values at ca. 2.5 eV are similar to inorganic semiconductor materials, suggesting potential applications in areas of photocatalysis and light-to-electricity conversion.