Porous {P6Mo18O73}-type Poly(oxometalate) Metal-Organic Frameworks for Improved Pseudocapacitance and Electrochemical Sensing Performance.

{P6Mo18} poly(oxometalate) (POM) clusters have huge steric hindrance and limited active oxygen atoms, which make them difficult to combine with metal-organic units to form three-dimensional (3D) porous structures. Therefore, functionalization of such POMs has always been a bottleneck that is difficult to break through. In this study, {P6Mo18} POM was successfully grafted on a lock-like metal-organic chain to generate a multiporous coordination polymer, [{Na(H2O)(H2btb)}{Cu4I(H2O)(pz)5Cl}{H2Sr⊂P6Mo2VMo16VIO73}]·3H2O (1) (pz = pyrazine; btb = 1,4-bis(1,2,4-triazole) butane). Meanwhile, a zero-dimensional (0-D) control compound with only btb ligands as counterions, (H4btb)[H4Sr⊂P6Mo2VMo16VIO73]·3H2O (2), was also obtained via a hydrothermal reaction. Compound 1 represents the first basket-type 3D poly(oxometalate) metal-organic framework (POMOF) assembly, which possesses interpenetrating pores and complex topology. 1-GO-CPE displays improved supercapacitor (SC) performance (the specific capacitance of 929.4 F g-1 at a current density of 3 A g-1 with 94.1% of cycle efficiency after 5000 cycles) compared with 2-GO-CPE and most reported POMOF electrode materials, which may be due to the outstanding redox capability of basket-POM, introduction of metal-organic chains, intersecting pores, and excellent conductivity of graphene. An asymmetric SC device with 1-GO-CPE as the negative electrode exhibits an energy density of 29.7 Wh kg-1 with a power density of 3148.2 W kg-1 and long-lasting cycling life. In addition, 1-GO-GCE as an electrochemical sensor responds to dopamine (DA) at a voltage of 0.40 V and shows lower detection limits (0.19 µM (signal-to-noise ratio (SNR) = 3)), higher selectivity, and good reproducibility in the linear range of 0.56 µM to 0.24 mM. The ability to accurately detect the content of DA in biological samples further proves the feasibility of the sensor in practical applications.

A Host-Guest Supercapacitor Electrode Material Based on a Mixed Hexa-Transition Metal Sandwiched Arsenotungstate Chain and Three-Dimensional Supramolecular Metal-Organic Networks with One-Dimensional Cavities.

The mixed hexa-transition metal (hexa-TM) sandwiched arsenotungstate derivative, [CuI3(pz)2(phen)3]2[CuI(phen)2][{Na(H2O)2}{(VIV5CuIIO6)(AsIIIW9O33)2}]·6H2O (1) (pz = pyrazine; phen = 1,10-phenanthroline), has been hydrothermally synthesized and structurally characterized. In compound 1, two {AsW9O33} clusters are connected by mixed hexa-TM ring unit {VVI5CuIIO6} to form a sandwich-type dimer, which are further bonded in "ABAB" mode by the {Na(H2O)2} linker resulting in pure inorganic chains. The unique "L-shaped" trinuclear complex {Cu3(phen)3(pz)2} is supported together via staggered π-π interactions to generate extending waveform two-dimensional supramolecular layers, which are further aggregated with their adjacent analogues by complexes {Cu(phen)2} via H-bonding interaction to yield an unprecedented three-dimensional (3D) metal-organic networks with one-dimensional (1D) cavities. The pure inorganic 1D sandwich chains are implanted in the cavities as guest units via supramolecular interactions to form a POMOF 3D framework. Compound 1, as the electrode of the supercapacitor, exhibits higher specific capacitances (825 F g-1 at a current density of 2.4 A g-1), better rate capability, more durable cyclic stability (91.4% of cycle efficiency after 3000 cycles), and improved conductivity and electroactivity compared to those of parent polyoxometalate (POM) Na9[AsW9O33]·19H2O (2) and 6-Cu-substituted POM [Cu6(imi)6{AsIIIW9O30Cl3}2]·6H2O (3), which may be attributed to the introduction of V4+, the unique host-guest structure, and the rich π electron system. In addition, compound 1 exhibits dual-function electrocatalytic behavior in reducing inorganic salt IO3- and oxidizing the organic molecule dopamine.

A novel method for sewage sludge composting using bamboo charcoal as a separating material.

Traditional composting processes must be conducted with a bulking agent to ensure adequate air space for aeration. The bulking agent and composting materials are always completely mixed. A novel layered structure was introduced in sewage sludge composting, in which no bulking agent was used and bamboo charcoal was used as a separating material. Three lab-scale composting reactors (A: sawdust and sludge; B: bamboo charcoal and sludge; and C: sawdust, bamboo charcoal, and sludge) were continuously operated for 29 days. Several physicochemical parameters were investigated to evaluate the feasibility of layered composting with bamboo charcoal. The results indicated that the maximum temperatures during the thermophilic stage in treatments A, B, and C were 51.4, 50.9, and 51 °C, respectively. Layered composting with bamboo charcoal decreased the pH of the thermophilic stage from 8.98 in A to 8.75 in C, and delayed the peaks by about 120 h. The degradation rates of dissolve organic carbon (DOC) and dissolved nitrogen (DN) were 75 and 71.5% in treatment B, respectively, which were significantly higher than those of control group A (60 and 59.1%, respectively). The total NH3 emissions of treatment C (2127.8 mg) were significantly lower than those of A (2522.8 mg). Our results suggested that layered composting using bamboo charcoal as a separating material could be an alternative strategy to the traditional composting method. Moreover, layered composting combined with sawdust could effectively reduce NH3 emissions and N loss.

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

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.

Synthesis and photo-/electro-catalytic properties of a 3D POMOF material based on an interpenetrated copper coordination polymer linked by in situ dual ligands and Dawson-type phosphotungstates.

A novel 3D polyoxometalate metal organic framework (POMOF), [{CuCu (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.

Organic-Inorganic Hybrid Materials Based on Basket-like {Ca⊂P6Mo18O73} Cages.

Four basket-like organic-inorganic hybrids, formulated as [{Cu(II)(H2O)2}{Ca4(H2O)4(HO0.5)3(en)2}{Ca⊂P6Mo4(V)Mo14(VI)O73}]·7H2O (1), (H4bth)[{Fe(II)(H2O)}{Ca⊂P6Mo18(VI)O73}]·4H2O (2), (H2bih)3[{Cu(II)(H2O)2}{Ca⊂P6Mo2(V)Mo16(VI)O73}]·2H2O (3), (H2bib)3[{Fe(II)(H2O)2}{Ca⊂P6Mo2(V) Mo16(VI)O73}]·4H2O (4), (bth = 1,6-bis(triazole)hexane; bih = 1,6-bis(imidazol)hexane; bib = 1,4-bis(imidazole)butane) have been hydrothermally synthesized and fully characterized. Compounds 1-4 contain polyoxoanion [Ca⊂P6Mon(V)Mo18-n(VI)O73]((6+n)-) (n = 0, 2, or 4) (abbreviated as {P6Mo18O73}) as a basic building block, which is composed of a "basket body" {P2Mo14} unit and a "handle"-liked {P4Mo4} fragment encasing an alkaline-earth metal Ca(2+) cation in the cage. Compound 1 exhibits an infrequent 2D layer structure linked by the Cu(H2O)2 linker and an uncommon tetranuclear calcium complex, while compound 2 is 8-connected 2-D layers connected by binuclear {Fe2(H2O)3} segaments, which are observed for the first time as 2-D basket-like assemblies. Compounds 3 and 4 are similar 1D Z-typed chains bonded by M(H2O)2 units (M = Cu for 3 and Fe for 4). The optical band gaps of 1-4 reveal their semiconductive natures. They exhibit universal highly efficient degradation ability for typical dyes such as methylene blue, methyl orange, and rhodamine B under UV light. The lifetime and catalysis mechanism of the catalysts have been investigated. The compounds also show good bifunctional electrocatalytic behavior for oxidation of amino acids and reduction of NO2(-).

Assembly of a basket-like {Sr ⊂ P6Mo18O73} cage from 0D dimmer to 2D network and its photo-/electro-catalytic properties.

A series of basket-like heteropoly blues, formulated as (H4bth)[{Cu(H2O)}2{Sr ⊂ P6MoV2MoVI16O73}]·4H2O (1), {H2bih}3[{FeII(H2O)2}{Sr ⊂ P6MoV2MoVI16O73}]·2H2O (2), (H2bih)3[{CoII(H2O)2}{Sr ⊂ P6MoV2MoVI16O73}]·2H2O (3), (H2bih)3[{NiII(H2O)2}{Sr ⊂ P6MoV2MoVI16O73}]·2H2O (4), (H2bih)2(H2bip)[{Zn (H2O)0.5}{Sr ⊂ P6MoV2MoVI16O73}]·5.5H2O (5), (bth = 1,6-bis(triazole)hexane; bih = 1,6-bis(imidazol)hexane; bip = 1,5-bis(imidazol)pentane) have been synthesized hydrothermally and fully characterized. The structural analysis shows that all the compounds contain two electron reduced polyanions [Sr ⊂ P6MoV2MoVI16O73]8− (abbreviated as {P6Mo18O73}), which consists of a tetra vacant γ-Dawson-type{P2Mo14} unit and a "handle"-shaped {P4Mo4} segment encapsulating a Sr2+ cation in the central cavity. Compound 1 is a 6-connected two-dimensional (2D) layer, which represents the first 2D assembly of basket-type polyoxometalates. Compounds 2­4 are isostructural one-dimensional zigzag chains linked by an M(H2O)2 linker (M = iron for 2, cobalt for 3, and nickel for 4). Compound 5 is a dimeric cluster supported by a binuclear {Zn2(H2O)} unit. The optical band gaps of 1­5 reveal their semiconductive natures. The compounds if used as photocatalysts exhibit a universal high efficiency degradation ability for dyes such as methylene blue, Rhodamine B, and Azon phloxine. The lifetime and reaction mechanism of the catalysts were investigated with a series of experiments. The compounds also show good bifunctional electrocatalytic behavior for the oxidation of ascorbic acid (AA) and reduction of nitrite ions.

Phosphorus metabolism and population dynamics in a biological phosphate-removal system with simultaneous anaerobic phosphate stripping.

In this study, the metabolism of phosphorus and changes in population dynamics were investigated via simultaneous chemical stripping in sidestream in an acetate-fed sequencing batch reactor. The synthesized intracellular polyphosphate (poly-P) by polyphosphate-accumulating organisms (PAOs) gradually decreased when the biomass was subjected to 83 d of P stripping. Initially, the P removal efficiency of the system improved from 94.3% to 96.9%. Thereafter, a relatively high level of P in effluent was observed, during which time the stoichiometric ratios of Prelease/HAcuptake decreased, Glycogendegraded/HAcuptake and poly-ß-hydroxyvalerate/PHA increased. The results revealed that a metabolic shift from polyphosphate-accumulating metabolism to glycogen-accumulating metabolism. Correspondingly, PAOs declined to less than 1% of the population, glycogen-accumulating organisms proliferated to almost 20% instead. The results of PCR­DGGE also indicated that the microbial community structure considerably changed in response to the gradually decreasing poly-P content. These findings imply that intracellular poly-P level is important for the stable of P removal system. Furthermore, it suggests that it is not a stable and effective way for P recycling from anaerobic stage of the biological P removal system in sidestream.