Four polyoxometalate-based semiconductive coordination polymers: Syntheses, structures, photoluminescent and photocatalytic properties

Four polyoxometalate-based semiconductive coordination polymers, namely, [Cd3(2,3′-Htmbpt)2(2,3′-tmbpt)4(γ-Mo8O26)(β-Mo8O26)(H2O)4]·5H2O (1), [Co(2,3′-Htmbpt)2(β-Mo8O26)]·4H2O (2), [Ag(2,3′-Htmbpt)2(β-Mo8O26)]·H3O·4H2O (3), and [Cu(2,3′-tmbpt)(β-Mo8O26)]·H2O (4) (2,3′-tmbpt = 1-((1H-1,2,4-triazol-1-yl)methyl)-3-(3-pyridyl)-5-(2-pyridyl)-1,2,4-triazole) have been synthesized under hydrothermal conditions. Their structures have been characterized by single-crystal X-ray diffraction analyses, infrared spectra (IR), elemental analyses and powder X-ray diffraction (PXRD) analyses. Polymer 1 has a 3D (4,6)-connected framework with (5·64·8)(4·52·62·7)(42·54·66·7·82) topology. In polymer 2, the [β-Mo8O26]4− anions connect the Co(II) ions to form a chain, which is decorated by the 2,3′-Htmbpt ligands. The chains are extended by the hydrogen bonding interactions to generate a 3D supramolecular framework. Polymer 3 displays a discrete structure, which is linked by the hydrogen bonding interactions to form a chain. The chains span in two different directions, yielding a plywood-like structure. In polymer 4, the [β-Mo8O26]4− anions connect the Cu(II) ions to furnish a layer, which is further coordinated by the 2,3′-Htmbpt ligands. The layers are linked by the hydrogen bonding interactions to form a 3D supramolecular framework. The optical band gaps of 1–4 reveal that they are potential semiconductive materials. The luminescent spectra of polymers 1 and 3 indicate that they emit blue luminescence at room temperature. The photocatalytic investigation indicates that polymers 1–3 can promote the decomposition of methylene blue solution, while polymer 4 inhibits the decomposition process.