Assembly of new organic–inorganic hybrids based on copper-bis(triazole) complexes and Keggin-type polyoxometalates with different negative charges

Three new organic–inorganic hybrid compounds based on copper-bis(triazole) complexes and Keggin-type polyoxometalates (POMs) with different negative charges, [Cu(I)BBTZ]3[PMo12O40] (1), [Cu(I)BBTZ][Cu(I)(HBBTZ)2][SiMo12O40]·2.5H2O (2) and [Cu(I)BBTZ]6[SiWV2WVI10O40]·2H2O (3) (BBTZ = 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene), have been hydrothermally prepared and characterized by elemental analyses, IR spectra, TG analyses, XPS spectra, powder X-ray diffraction and single-crystal X-ray diffraction analyses. Compounds 1 and 2 exhibit the POM-templated 3D host–guest supramolecular frameworks. Compound 3 displays a POM-supported 3D open framework. In these three hybrid compounds, the structural transformation from host–guest framework to open framework were modulated by the introduction of Keggin-type polyoxoanions with different negative charges. Moreover, the electrochemical properties of compounds 1–3 were investigated and all these compounds show the electrocatalytic activities towards the reduction of nitrite.