Three Keggin POMs-based coordination polymers constructed by linear N-heterocyclic ligand for proton conduction, photocatalytic activity and magnetic property

Abstract

POMs-based coordination polymers are promising materials for their potential application in the fields of proton conduction, catalysis and magnetism. Three new coordination polymers namely, {[Co2(bib)3(H2O)2(H4W12O40)]·7H2O}n (1), {[Zn3(bib)8(H3ZnW12O40)2]·12H2O}n (2) and {[Ag5(bib)5(H3W12O40)]·5H2O}n (3) were synthesized under hydrothermal conditions based on linear nitrogen heterocyclic ligand 1,4-bis(1-imidazolyl)benzene (bib). In compound 1, CoII ions are linked with [H4W12O40]4– anions to form a planar network and can be simplified as kgd topology, which are further linked with bib ligands to form a 3D framework. Zn2 ions of compound 2 alternately connect with bib ligands and [H3ZnW12O40]3– anions to form 1D chain structure, while Zn1 ion forms isolated unit with three bib ligands and one [H3ZnW12O40]3– anion, and a 3D framework is finally constructed through π … π stacking interactions. In compound 3, the 3D structure is constructed from a number of 1D chains formed by AgI ions and bib ligands in different directions through π … π stacking interaction and Ag⋯O weak connection. The proton conductivity of 1–3 are 2.03 ​× ​10−5, 1.04 ​× ​10−6 and 1.87 ​× ​10−4 ​S ​cm−1 at 98% RH and 358 ​K, respectively. In addition, compounds 1–3 exhibit photocatalytic degradation capacity towards RhB and compound 1 displays antiferromagnetic behavior.