Calix[4]arene-based polyoxometalate organic–inorganic hybrid and coordination polymer as heterogeneous catalysts for azide–alkyne cycloaddition and Knoevenagel condensation reaction

Abstract

Based on a neutral pyridyl-functional calix[4]arene ligand (L = tetrakis [(3-pyridylmethyl)oxy]-p-tertbutylcalix[4]arene), one polyoxometalate-based organic–inorganic hybrid [Cu₂L(SiW₁₂O₄₀)_0.5]·CH₃CN·2H₂O (1) and one coordination polymer [CdCl₂L]·CH₃CN (2) have been successfully synthesized under solvothermal conditions. 1 exhibits a distinctive layer attributed to the weak interactions among the positive Cu(I)–L chains and [SiW₁₂O₄₀]⁴ anions. 2 displays a chain model containing a Cd(II) dimer. Both 1 and 2 were investigated as heterogeneous catalysts. 1 is an excellent heterogeneous catalyst for the azide–alkyne cycloaddition (AAC) reaction and 2 exhibits highly efficient catalytic performance for the Knoevenagel condensation reaction. Both 1 and 2 were easily separated.