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Two novel Wells–Dawson polyoxometalate-based compounds, (H2bimb)2[{Ag1.5(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. [ABSTRACT FROM AUTHOR]

Herein, a new 3D POMOF [{Cl4Cu10(pz)11}{As2W18O62}]·1.5H2O (pz = pyrazine) (1) has been synthesized using a hydrothermal reaction, and characterized by single-crystal X-ray diffraction analysis, elemental analysis, IR, TG, and UV-vis-NIR spectroscopy, XPS, BET analysis and XRD. Single crystal X-ray analysis reveals that compound 1 consists of the classical Wells–Dawson [As2W18O62]6− polyoxoanion and {Cl4Cu10(pz)11} complexes. Compound 1 possesses two different channels which form a 3D topology framework with the Schläfli symbol of {3·4·56·67}2{3·46·53}2{32·42·56·65}. Additionally, compound 1 shows photoluminescence properties and excellent photocatalytic activity for the degradation of RhB dye under UV irradiation. The photocatalytic reaction kinetics and mechanism have been also investigated. [ABSTRACT FROM AUTHOR]

Herein, five Keggin polyanion-templated inorganic–organic hybrids, (H3biz)4[SiMo12O40] (1), (H3biz)3(H2biz)[PMo12O40] (2), [{Cu7(Hbtz)2(btz)4}{PMo12O40}] (3), [{Ag7(Hbtz)2(btz)4}{AsW12O40}] (4), and [{Ag9(H2biz)2(biz)4} {H2PW12O40}] (5) (H2biz = benzimidazole, Hbtz = benzotriazole) were hydrothermally synthesized and characterized via elemental analysis, thermogravimetry (TG), infrared spectroscopy (IR), ultraviolet spectroscopy (UV), and single-crystal X-ray diffraction. A remarkable aspect of compound 1 is that six pairs of H2biz ligands are circularly arranged around the {SiMo12} cluster; this leads to the formation of a unique 2-D supramolecular layer. The most prominent feature of the structure of compound 2 is that protonated Hbiz ligands link the {PMo12} cluster into hexagonal units, which are further extended into a 2-D supramolecular array via edge-sharing modes. The Keggin {PMo12} and {AsW12} clusters in compound 3 and 4 are first extended into octa-connected 2-D sheets by the unusual heptanuclear complex {M7(Hbtz)2(btz)4} (M = Cu for 3 and Ag for 4) linker. Interestingly, two types of M–M interactions exist in the heptanuclear units. Compound 5 exhibits an unprecedented 2D network constructed from nine-nuclear silver complex {Ag9(biz)4(H3biz)2} bridges and {PW12} clusters. Most strikingly, carbene silver and the coexistence of multiple Ag–C bonds are first observed in the nine-nuclear unit. Intensive CuI/AgI–π interactions and π–π stacking play important roles in the packing arrangements of 3–5. Additionally, the electrochemical, electrocatalytic, fluorescence, and photocatalytic properties of 1–5 have been investigated in detail. [ABSTRACT FROM AUTHOR]

A novel 3D polyoxometalate metal organic framework (POMOF), [{CuII6CuI10 (H2O)5(pzc)10(pz)6}{P2W18O62}2]·4H2O (1) (Hpzc = pyrazine-2-carboxylic acid, pz = pyrazine) has been hydrothermally synthesized and characterized by IR, TG, XRD, UV-vis and elemental analyses. In compound 1, the pzc and pz ligands are generated through in situ transformation from pyrazine-2,3-dicarboxylic acid (pzdc) to remove one or two CO2 molecules. The ligands with four coordination modes connect nine crystallographically independent Cu atoms to form a super-big circle unit. Each ring unit is connected to the adjacent six rings via an edge-sharing way to form a 2-D Cu/pz/pzc MOF layer, which is further extended along two spatial directions by two kinds of insert modes to generate an interpenetrating and staggered 3-D metal organic network. The {P2W18} clusters as nine-node inorganic guest molecules are grafted on the Cu/pz/pzc framework forming a complex 3D POMOF with a new topology {4·6·83·10}2 {4·6·8}2 {4·62·82·10}2{4·63·82}2{4·85}2{42·62·82}2{42·63·8}{43·67·813·1010·123}2 {4}6{6·82}2{62·8}2 {64·8·10}{6}2{8}4. Additionally, compound 1 exhibits good electrocatalytic activity for the reduction of H2O2 and effective photocatalytic degradation ability for three azo dyes under UV irradiation. [ABSTRACT FROM AUTHOR]

The arsenomolybdates [H2As2Mo6O26(H2O)]·(H2biyb)2· 2H2O (1) and [H3As2Mo6O26]·(H3pt)2 (2) [biyb = 1,4-bis(imidazol-1-ylmethyl)benzene, pt = 4'-(3"-pyridyl)-2,3':6'3"-terpyridine] were synthesized via hydrothermal method. The structures of the compounds were characterized by single-crystal X-ray diffraction analyses, elemental analyses, IR spectroscopy, and TG analysis. Compounds 1 and 2 exhibit two isomeric forms of [HxAs2Mo6O26](6-x)-. The structure of 1 is constructed from the B-type [H2As2Mo6O26(H2O)]4- poly-anions and free biyb ligands via weak interactions to form 3D supramolecular framework with a {3·4·5³·6}{3·4³·5²}{3·5·6}2{3·5²}² topology structure. In compound 2, the A-type [H3As2Mo6O26]3- clusters are surrounded by pt ligands through hydrogen bond interactions forming 3D supramolecular framework with a {4³·6³}²{46·66·8³} topology structure. The electrochemical behaviors, electrocatalytic and photocatalytic activities of 1 and 2 are detected. [ABSTRACT FROM AUTHOR]

Herein, two Wells –Dawson-type arsenomolybdates, formulated as [Cu(pyr)2]6[As2Mo18O62] (1) and [Ag(pyr)2]6[As2Mo18O62] (2) (pyr = pyrazole), were hydrothermally synthesized and structurally characterized via single-crystal X-ray diffraction, elemental analysis, IR and UV-vis-NIR spectroscopies, XPS, XRD, and TG analysis. The structural analysis indicated that compounds 1 and 2 were isomorphic. They are the first reported 3D honeycomb structures of Wells–Dawson-type arsenomolybdates. The [M(pyr)2] (M = Cu and Ag) connected with [As2Mo18O62]6− polyoxoanions to form the {812·123}{8}3 topological structure. The contributions of organic ligands, pH value, reaction temperature, and transition-metal (TM) to the construction of 3D networks were elucidated. Furthermore, compounds 1 and 2 exhibited fluorescence properties in the solid state at room temperature, highly efficient catalytic ability for the degradation of five organic dyes (MB, RhB, MO, AP, and CR) under UV irradiation, and obvious electrocatalytic activities for the reduction of H2O2. The mechanisms of photocatalysis and electrocatalysis have also been discussed in detail. [ABSTRACT FROM AUTHOR]

A series of organic–inorganic hybrid compounds, [{Cu(4,4′-bipy)1.5(H2O)2}2{H2As2Mo6O26}] (1), [{Cu (biim)2}2{HAs2Mo6O26}{Cu(biim)Cl}]·H2O (2), (H2bib)[{Cu(H2O)2(bib)}{H2As2Mo6O26}]·2H2O (3), [{(Hbix)Cu(bix)0.5}2{As2Mo6O26}]·2H2O (4), [{Cu(bmb)1.5(H2O)}2{H2As2Mo6O26}]·2H2O (5), 0 and [{Cu2(bth)4}{H2As2Mo6O26}]·H2O (6) (4,4′-bipy = 4,4′-bipyridine; biim = biimidazole; bib = 1,4-bis(1-imidazolyl)benzene; bix = 1,4-bis(imidazol-1-ylmethyl)benzene; bmb = 1,4-bis(benzimidazol-1-yl)benzene; bth = 1,6-bis(1,2,4-triazol-lyl)hexane), were hydro-thermally synthesized and structurally characterized via elemental analysis, TG, IR, XPS, XRD, and single-crystal X-ray diffraction. The crystal structures 1–6 are formed by metal–organic complexes and the [HxAs2Mo6O26](6−x)− cluster. Compounds 1–2 feature infinite 1D-chain structures. Compounds 3–5 form 2D-layer structures in which Cu cations are five-, six-coordinated with polyoxoanions and organic ligands. Notably, compound 6 introduces the POM system into a metal–organic framework (MOF) to form a unique POMOF {42·611·82}{42·64}{44·69·7·8} topological structure. The coordination modes of the [HxAs2Mo6O26](6−x)− cluster in compounds 2, 5 and 6 are reported for the first time. The photocatalytic properties of 1–6 are studied for the decomposition of methylene blue (MB) under UV light. In addition, all the compounds exhibit good electrocatalytic performances for the reduction of nitrite. [ABSTRACT FROM AUTHOR]