Syntheses, structures, and properties of a series of supramolecular hybrids based on Keggin or Wells–Dawson polyoxometalates and 4,4′-bipyridines

Three new organic–inorganic supramolecular hybrids, namely, [4,4′-Hbpy]2[HPW12O40]·H2O (4,4′-bpy = 4,4′-bipyridine, 1), [4,4′-H2bpy]6[P2W18O62]2·6H2O (2), [4,4′-H2bpy]5[HP2W18O62]2 (3), were hydrothermally synthesized in situ at different pH. Single crystal X-ray diffraction analyses show that complex 1 constructed from Keggin polyoxoanions and 4,4′-bipyridine organic ligands, exhibits an extended three-dimensional supramolecular network via hydrogen bonding, while 3D supramolecular network of complexes 2–3 were based on Wells–Dawson polyoxoanions and 4,4′-bipyridine organic ligands. The structural differences of complexes 1–3 indicated that the self-assembly process is pH-dependent. Complexes 1–3 have good photocatalytic activity for the photodegradation of methyl orange in the presence of H2O2 under UV light irradiation.