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Two novel Anderson-type polyoxometalates (POMs)-based metal-organic frameworks (MOFs), namely, H{Cu2(μ2-OH)2L¹[CrMo6(OH)6O18]}·4H2O (1), {Cu2L²[CrMoVI 5MoV(OH)6O18](H2O)4}·4H2O (2) (L¹ = N,N'-bis(3-pyridinecarboxamide)-piperazine, L² = N,N'-bis(4-pyridinecarboxamide)-piperazine), are hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction, IR spectra, powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). In complex 1, the hexadentate [CrMo6(OH)6O18]3- polyoxoanion bridges the CuII ions to generate a 2D Cu-POM inorganic layer, which is further extended by the μ2-bridging L¹ ligands (via ligation of pyridyl nitrogen atoms) to form a 3D MOF with a 4,6-connected {44·610·8}{44·6²} topology. Complex 2 is also a 3D POM-based MOF exhibiting a {42·84} topology, which is constructed from the quadridentate [CrMoVI 5MoV(OH)6O18]4- polyoxoanions and μ4-bridging L² ligands (via ligation of pyridyl nitrogen and carbonyl oxygen atoms). The different coordination modes of POM polyanions and the isomeric bis(pyridylformyl)piperazine ligands play key roles in the construction of the title complexes. In addition, the photocatalytic activities of the title complexes on the degradation of methylene blue (MB) under UV, visible light and sunlight irradiation have been investigated in detail. [ABSTRACT FROM AUTHOR]

Three octamolybdate-based metal-organic complexes (MOCs), namely, [H2en]2[Cu(pzca)2(Mo8O26)]. 4H2O (1), [Cu2(pzca)2(Mo8O26)0.5(H2O)4].H2O (2) and [CuI 3CuII 4(pzca)7(Mo8O26)(H2O)2].4H2O (3) (en = ethylenediamine, pzca = 2-pyrazinecarboxylic acid), have been successfully synthesized under hydrothermal conditions via adding different kinds of amine and adjusting the pH values. The single crystal X-ray diffraction, elemental analyses, IR spectra, and thermogravimetric analyses have been used to characterize the title complexes. In compound 1, the [Cu(pzca)2] units bridge the [β-Mo8O26]4- clusters to generate a 1D chain, which is extended by hydrogen-bonding interactions to a 3D supramolecular structure. Compound 2 exhibits a 3D coordination framework based on the 1D infinite [Cu2(pzca)2]n2n+ zigzag chains and β-Mo8O26 4- anions, and shows a trinodal 3,3,4-connected {83}4{86} topology containing a dodecagonal channel with the dimension of 13.496 × 19.642 Å2. Compound 3 is a 3D metal-organic network derived from the "λ"-like [Cu5(pzca)4] subunits and [β-Mo8O26]4- anions, which represents a novel {4.6.83.10}2{4.6.8}2{42.104}{42.83.10}{6.82}2{62.103.12}{62.82.102}{62.83.10}{63}4 topology in octamolybdate- based MOCs. The structural diversities show that the different amines and pH value of the reaction system play key roles in the construction of high dimensional architectures. Moreover, the electrochemical behaviors and photocatalytic activity for compound 1 have been investigated in detail. [ABSTRACT FROM AUTHOR]