Efficient and robust photocatalysts based on {P₂W₁₈} modified by an Ag complex

Two novel Wells-Dawson polyoxometalate-based compounds, (H₂bimb)₂[{Ag_1.5(bimb)_1.5}(P₂W₁₈O₆₂)] (1), (H₂bimb)₂[Ag(bimb)]_0.5[Ag(eim)₂]_0.5[P₂W₁₈O₆₂]·H₃O (2) (bimb = 1,4-bis(imidazole-l-yl)butane, eim = ethyl(imidazole)), have been synthesized under hydrothermal conditions and characterized by IR, thermogravimetric, XRD and single-crystal X-ray diffraction analyses. In compound 1, two "U"-type bimb ligands are connected together viaπ interactions of Ag-C to form a ring unit. The ring unit alternately links with the "Z"-type bimb via an Ag-N bond to form an infinite Z-shaped {Ag₄(bimb)₃}_n chain. The adjacent two {P₂W₁₈} clusters bonded to two Ag1 ions on two adjacent Z-shaped chains to form an inorganic dimer linker, which further joins the Z-shaped chains together, resulting in unique organic-inorganic alternating 2-D layers. Adjacent 2D layers are further aggregated together via Ag-O bonds between the Dawson cluster and the Z-type chain on different layers to yield a 3-D network with a new topology {10³}₂{10}{4·10²}₄{4²·10⁴}₂. In compound 2, the eim ligand was synthesized in situ from bimb, which acts as a small molecular ligand to alter the structure and adjust the catalytic activity of compound 2. Each Ag2 connects with the bimb ligand to form a linear {Ag(bimb)} chain. Adjacent chains are bonded together via the bimb ligand to generate a supermolecule 2-D layer, in which a Dawson dimer cluster as a guest molecule is embedded in both sides of the layer through supermolecule interactions. Such 2-D layers are further supported by Ag(eim)₂ units leading to 3D supermolecule nets. In addition, the compounds exhibit excellent electrocatalytic behavior and better photocatalytic degradation capability for typical dyes than other Wells-Dawson POMs.