Modified polyoxometalate: a novel monocapped bi-supporting and reduced α-Keggin structure...

A novel modified polyoxometalate, {PMo₁₂O₄₀[Cu(2,2'-bpy)]}[Cu(2,2'-bpy)(en)(H₂O)]₂ [2,2'-bpy is 2,2'-bipyridyl (C₁₀H₈N₂) and en is ethylenediamine (C₂H₈N₂)], has been synthesized hydrothermally and structurally characterized by elemental analysis, TG, IR, XPS and single-crystal X-ray diffraction. The structural analysis reveals that the compound contains the reduced Keggin polyanion [PMo₁₂O₄₀]^6- as the parent unit, which is monocapped by [Cu(2,2'-bpy)]²⁺ fragments via four bridging O atoms on an {Mo₄O₄} pit and bi-supported by two [Cu(2,2'-bpy)(en)(H₂O)]²⁺ coordination cations simultaneously. There exist strong intramolecular π-π stacking between the capping and supporting units, which play a stabilizing role during the crystallization of the compound. Adjacent POM clusters are further aggregated to form a three-dimensional supramolecular network through noncovalent forces, hydrogen bonding and π-π stacking interactions. In addition, the photocatalytic properties were investigated in detail, and the results indicated that the compound can be used as a photocatalyst towards the decomposition of the organic pollutant methylene blue (MB).