Two polyoxometalate-based CuII complexes with a new semi-rigid bis (pyrazine)-bis(amide) ligand: Architectures, adsorption activities for dyes and bifunctional electrocatalytic performances

Two new polyoxometalates (POMs)-based metal-organic complexes (MOCs), formula as [Cu-2(L)(2)SiW12O40] (1), [Cu(L)(beta-Mo8O26)(0.5)]center dot H2O (2) [L = N,N'-bis(2-pyrazinecarboxamide)-1,2-cyclohexane] have been prepared by using a new semi-rigid bis(pyrazine)-bis(amide) ligand under the hydrothermal conditions. Crystal analysis reveals that complex 1 is a 2D supramolecular structure based on the 1D [CuL](n)(2n)+ chains, in which the [SiW12O40](4)(SiW12) anions serve as noncoordinated templates. Complex 2 is a 2D network, which is composed of the bidentate bridging [beta-Mo8O26](4) (Mo-8) anions and 1D [CuL](n)(2n+) chains. Both 1-2 display excellent adsorption behaviors and can effectively adsorb organic dyes methylene blue (MB) and gentian violet (GV). It is worth mentioning that 1-2 were hardly changed after three cycles of the adsorption-desorption process. In addition, the bifunctional electrocatalytic performances of complex 1-2 were also studied in detail. The different architectures and properties of 1-2 were induced by diverse POM anions.