Assembly of polyoxometalate-thiacalix[4]arene-based inorganic–organic hybrids as efficient catalytic oxidation desulfurization catalysts

Abstract

Self-assembly of polyoxometalates, Ni(II)/Ag(I) cations and tetra-[5-(mercapto)-1-methyltetrazole]-thiacalix[4]arene (L) yielded three inorganic–organic hybrids, namely, [Ni₃L₂(CH₃OH)₆(H₂O)₄][PMo₁₂O₄₀]₂·3CH₃OH·2H₂O (1), [Ni₃L₂(CH₃OH)₆(H₂O)₄][PW₁₂O₄₀]₂·3CH₃OH·2H₂O (2) and [Ag₃L(PMo₁₂O₄₀)] (3). In hybrids (1) and (2), Ni(II) cations are linked by L ligands to produce layered frameworks, and H bonds among the [PMo₁₂O₄₀]³⁻/[PW₁₂O₄₀]³⁻ anions and L ligands lengthen the structures to form 3D supramolecular architectures. Hybrid (3) exhibits a 3D architecture, of which Ag(I) cations not only coordinated with the N and O atoms of L ligands and [PMo₁₂O₄₀]³⁻ anions simultaneously, but also connected each other by Ag–Ag interactions. It is worth mentioning that 1 and 3 as recyclable catalysts show excellent heterogeneous catalytic activity in oxidation desulfurization reactions.