A host-guest compound formed by Cu3[P2W18O62] and HKUST-1 with capacitance and H2O2 sensing properties.

Polyoxometalate-based metal-organic frameworks (POMOFs) have received wide attention in supercapacitors and H2O2 detection due to their possession of the rich redox active sites of polyoxometalates (POMs) and the ordered structure of metal-organic frameworks (MOFs). In this study, we successfully synthesized a host-guest Cu3[P2W18O62]@HKUST-1 (HRBNU-7) compound by a grinding method. Cu3[P2W18O62] successfully entered the HKUST-1 pores as confirmed by the results of infrared (IR) spectroscopy, powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The specific capacitance of HRBNU-7 is 318.6 F g-1 at 1 A g-1 in a three-electrode system using nickel foam as the collector. The specific capacity retention is 92.36% after 5000 cycles. The assembled symmetrical supercapacitor (SSC) achieved a high energy density of 10.58 W h kg-1 at a power density of 500.00 W kg-1. In addition, HRBNU-7 exhibits excellent electrochemical detection of H2O2, including a wide linear range of 0.5 µM-0.3 mM, a low detection limit of 0.17 µM, and excellent selectivity and stability, and it can be effectively utilized for the analysis of H2O2 content in actual serum samples. These excellent properties are attributed to the unique redox activity of Cu3[P2W18O62] and the high specific surface area of HKUST-1. This work offers a strategy for exploring POMOFs as electrode materials in supercapacitors and electrochemical sensors.

Nanomaterial with Core-Shell Structure Composed of {P2W18O62} and Cobalt Homobenzotrizoate for Supercapacitors and H2O2-Sensing Applications.

Designing and preparing dual-functional Dawson-type polyoxometalate-based metal-organic framework (POMOF) energy storage materials is challenging. Here, the Dawson-type POMOF nanomaterial with the molecular formula CoK4[P2W18O62]@Co3(btc)2 (abbreviated as {P2W18}@Co-BTC, H3btc = 1,3,5-benzylcarboxylic acid) was prepared using a solid-phase grinding method. XRD, SEM, TEM et al. analyses prove that this nanomaterial has a core-shell structure of Co-BTC wrapping around the {P2W18}. In the three-electrode system, it was found that {P2W18}@Co-BTC has the best supercapacitance performance, with a specific capacitance of 490.7 F g-1 (1 A g-1) and good stability, compared to nanomaterials synthesized with different feedstock ratios and two precursors. In the symmetrical double-electrode system, both the power density (800.00 W kg-1) and the energy density (11.36 Wh kg-1) are greater. In addition, as the electrode material for the H2O2 sensor, {P2W18}@Co-BTC also exhibits a better H2O2-sensing performance, such as a wide linear range (1.9 µM-1.67 mM), low detection limit (0.633 µM), high selectivity, stability (92.4%) and high recovery for the detection of H2O2 in human serum samples. This study provides a new strategy for the development of Dawson-type POMOF nanomaterial compounds.

An inorganic-organic hybrid nanomaterial with a core-shell structure constructed by using Mn-BTC and Ag5[BW12O40] for supercapacitors and photocatalytic dye degradation.

Creating inorganic-organic hybrids with polyoxometalates (POMs) and metal-organic frameworks (MOFs) as energy storage and dye-degradation materials remains challenging. Here, a new hybrid nanomaterial Mn-BTC@Ag5[BW12O40] is synthesized by using Ag5[BW12O40] and Mn3(BTC)2(H2O)6 (Mn-BTC, BTC = 1,3,5-benzenetricarboxylic acid) through a plain grinding method. The structure and morphology characterization by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), and transmission electron microscopy (TEM) shows that the synthetic products have core-shell construction. Due to its unique structure wherein the core is Mn-BTC and the shell is Ag5[BW12O40], it exhibits excellent capacitance performance. In a three-electrode system where nickel foam is a collector, at a current density of 1 A g-1, its specific capacitance is 198.09 F g-1; after 5000 cycles, the capacitance retention rate is 94.4%. When the power density is 503.1 W kg-1, the symmetrical supercapacitor reveals a high energy density which is 10.9 W h kg-1. At the same time, the capacitance retention is 92.9% after 5000 cycles which showed good cycle stability. The photocatalytic degradation efficiencies of rhodamine B (RhB), methyl orange (MO) and methylene blue (MB) dyes exceed 90% after 140 min, and the degradation results remained unchanged after five photocatalytic cycles. The photocatalytic degradation mechanism shows that ˙OH has a major effect. The results show that this research provides a fresh idea for the development of energy storage and dye photocatalytic degradation materials.

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.

{BW12O40} Hybrids Modified by in Situ Synthesized Rigid Ligand with Supercapacitance and Photocatalytic Properties.

Organic rigid ligand-modified polyoxometalate-based materials possess complex and diverse structures, promising electrochemical energy storage properties and outstanding photocatalytic capabilities. Hence, two new [BW12O40]5-(abbreviated as {BW12O40})-based inorganic-organic hybrids [{Cu(en)2(H2O)}][{Cu(pdc)(en)}{Cu(en)2}(BW12O40)]·2H2O (1) and [{CuI5(pz)6(H2O)4}(BW12O40)] (2) (pdc = 2-picolinate, en = ethylenediamine, pz = pyrazine) were successfully synthesized through a hydrothermal method. Among them, pdc and pz were obtained by in situ transformation from 2,6-pyridinedicarboxylic acid (H2 pydc) and 2,3-pyrazinedicarboxylic acid (H2pzdc), respectively. In compound 1, the {BW12O40} clusters as an intermediate junction connect with {Cu(pdc)(en)}{Cu(en)2} and {Cu(en)2(H2O)} to form monomers, which in turn form supramolecular chains, sheets, and space network via hydrogen bonding. The {BW12O40} clusters are packed into copper-pyrazine frameworks in compound 2, and a unique polyoxometalate-based metal organic frameworks (POMOFs) structure with a new topology of {12}2{6.123.142}2{62.12.142.18}{62.123.16}{6}6 is formed via covalent bonds. When used as electrode materials for supercapacitors, the values of specific capacitance are 651.56 F g-1 for 1-GCE and 584.43 F g-1 for 2-GCE at a current density of 2.16 A g-1 and good cycling stability (90.94%, 94.81% of the initial capacity after 5000 cycles at 15.12 A g-1, respectively). The kinetic analysis reveals that surface capacitance plays a major role. Furthermore, both compounds can effectively degrade Rhodamine B (RhB) and Methylene blue (MB), showing the outstanding photocatalytic performance.

Cu/Ag Complex Modified Keggin-Type Coordination Polymers for Improved Electrochemical Capacitance, Dual-Function Electrocatalysis, and Sensing Performance.

Different metal-organic units were introduced into the {PMo12} polyoxometalate (POM) system to yield three porous coordination polymers with distinct characteristics, {Cu(pra)2}[{Cu(pra)2}3{PMo11VIMoVO40}] (1), [{Ag5(pz)6(H2O)0.5Cl}{PMo11VIMoVO40}] (2), and [{Cu3(bpz)5(H2O)}{PMo12O40}] (3) (pra = pyrazole; pz = pyrazine; bpz = benzopyrazine), via an in situ hydrothermal method. In comparison with the maternal Keggin cluster and most reported POM electrode materials, compounds 1-3 exhibit larger specific capacitances (672.2, 782.1, and 765.2 F g-1 at a current density of 2.4 A g-1, respectively), superior cyclic stability (91.5%, 89.3%, and 87.8% of cycle efficiency after 5000 cycles, respectively), and boosted conductivity, which may be attributed to the introduction of metal-organic units. The result indicates that metal-organic units can effectively enhance the capacitance performance of POMs. This may be due to the fact that they provide additional redox centers, induce the formation of stable porous structures, and improve ion/electron transfer efficiency. Compounds 1-3 present excellent electrocatalytic activity in reducing peroxide (H2O2) and oxidizing ascorbic acid (AA). In addition, compound 2 shows an outstanding sensing performance detection of AA and H2O2.

{BiW8 O30 } Exerts Antitumor Effect by Triggering Pyroptosis and Upregulating Reactive Oxygen Species.

We successfully synthesized {BiW8 }, a 10-nuclear heteroatom cluster modified {BiW8 O30 }. At 24 h post-incubation, the IC50 values of {BiW8 } against HUVEC, MG63, RD, Hep3B, HepG2, and MCF7 cells were 895.8, 127.3, 344.3, 455.0, 781.3, and 206.3 µM, respectively. The IC50 value of {BiW8 } on the MG63 cells was more than 2-fold lower than that of the other raw materials. Through morphological and functional features, we demonstrated pyroptosis as a newly identified mechanism of cell death induced by {BiW8 }. {BiW8 } increased 2-fold reactive oxygen species (ROS) levels in MG63 cells at 24 h post-incubation. Compared with 0 h, the glutathione (GSH) content decreased by 59, 65, 75, 94, and 97 % at 6, 12, 24, 36 and 48 h post-incubation, respectively. Furthermore, multiple antitumor mechanisms of {BiW8 } were identified via transcriptome analysis and chemical simulation, including activation of pyroptosis, suppression of GSH generation, depletion of GSH, and inhibition of DNA repair.

Wells-Dawson Arsenotungstate Porous Derivatives for Electrochemical Supercapacitor Electrodes and Electrocatalytically Active Materials.

Two Wells-Dawson arsenotungstate coordination polymers, [{CuII(bim)2}3(As2W18O62)] (1) and [(CuI10pz10Cl4)(As2W18O62)] (bim = 2,2'-biimidazole; pz = pyrazine), have been assembled via a hydrothermal method and fully characterized. Compound 1 exhibits a 2,6-connected two-dimensional hybrid layer based on asymmetrically modified {As2W18} anions and {Cu(bim)2} linkers, which is extended to a three-dimensional network with a special interlayer structure and a one-dimensional tunnel. Compound 2 is a host-guest framework that consists of a Cu-pz-Cl network with 20-member square rings, 16-member irregular rings, and embedded eight-node {As2W18} guest molecules. Compounds 1 and 2 show uncommon specific capacitance (834.8 and 960.1 F g-1, respectively, at a current density of 2.4 A g-1), enduring cycling stability (capacitance retention rates of 89.3% and 91.9%, respectively, after 5000 cycles), and good electrical conductivity, which are superior to those of the unmodified zero-dimensional Dawson arsenotungstate compound and most reported electrode materials in terms of their stable structure, special layer spacing, and orderly channels. Moreover, the title compounds exhibit excellent electrocatalytic activity for oxidizing ascorbic acid and reducing nitrite.

Inhibition of Mitochondrial ATP Synthesis and Regulation of Oxidative Stress Based on {SbW8 O30 } Determined by Single-Cell Proteomics Analysis.

The 10-nuclear heteroatom cluster modified {SbW8 O30 } was successfully synthesized and exhibited inhibitory activity (IC50 =0.29 µM). Based on proteomics analysis, Na4 Ni2 Sb2 W2 -SbW8 inhibited ATP production by affecting the expression of 16 related proteins, hindering metabolic functions in vivo and cell proliferation due to reactive oxygen species (ROS) stress. In particular, the low expression of FAD/FMN-binding redox enzymes (relative expression ratio of the experimental group to the control=0.43843) could be attributed to the redox mechanism of Na4 Ni2 Sb2 W2 -SbW8 , which was consistent with the effect of polyoxometalates (POMs) and FMN-binding proteins on ATP formation. An electrochemical study showed that Na4 Ni2 Sb2 W2 -SbW8 combined with FMN to form Na4 Ni2 Sb2 W2 -SbW8 -2FMN complex through a one-electron process of the W atoms. Na4 Ni2 Sb2 W2 -SbW8 acted as catalase and glutathione peroxidase to protect the cell from ROS stress, and the inhibition rates were 63.3 % at 1.77 µM of NADPH and 86.06 % at 10.62 µM of 2-hydroxyterephthalic acid. Overall, our results showed that POMs can be specific oxidative/antioxidant regulatory agents.

Multinuclear Transition Metal Sandwich-Type Polytungstate Derivatives for Enhanced Electrochemical Energy Storage and Bifunctional Electrocatalysis Performances.

Different transition metal (TM) units are introduced into a trivacant Keggin cluster to form three sandwich polytungstate derivatives, (H2en)[{K(H2O)0.5}2{K2(H2O)3}{Ni(H2O)(en)2}2{Ni4(H2O)2(PW9O34)2}] (1), [Cu6(Himi)6{AsIIIW9O33}2]·5H2O (2), and (H2btp)4[FeIII2FeII2(H2O)2(AsW9 O34)2]·4H2O (3) (en = ethanediamine; imi = imidazole; btp = 1,3-bis(1, 2, 4-triazol-1-yl) propane). Compound 1 is a 2,3,8-connected 3D network with {43}2{46·66·83·612·8}{6}2 topology based on bisupported tetra-Ni sandwich phosphotungstate and two kinds of potassium connection units. Compound 2 is a dense 12-connected 3D supramolecular network with {324·436·56} topology based on hexa-Cu(imi) sandwiched arsenotungstate. Compound 3 represents the first mixed valence tetra-Fe substituted sandwich arsenotungstate assembly. Compounds 1-3 show enhanced supercapacitor performance (618.2, 603.4, and 504.6 F·g-1 at a current density of 2.4 A·g-1 with 91.5%, 89.3%, and 87.8% of cycle efficiency after 5000 cycles, respectively) compared to their maternal polyoxometalates (POMs) and most reported POM-based electrode materials, which suggests that the introduction of multinuclear TM into vacant POMs is an effective method to improve the energy storage performance of POMs. In addition, compounds 1 and 3 exhibit dual-functional electrocatalytic behaviors in the reduction of iodate and the oxidation of dopamine for introduction of {Ni4} and {Fe4} units.

A Facile Grinding Method for the Synthesis of 3D Ag Metal-Organic Frameworks (MOFs) Containing Ag6 Mo7 O24 for High-Performance Supercapacitors.

Successful synthesis of three kinds of dynamically stable compounds by a simple grinding method is reported, giving Ag6 Mo7 O24 , Ag-BTC (Ag-MOF, BTC=benzene-1,3,5-tricarboxylic acid), and {Ag6 Mo7 O24 }@Ag-MOF metal-organic frameworks (MOFs). According to the electrochemical dynamic analysis, these materials have pseudocapacitor behavior and high capacitance. The unique nanorod structure of {Ag6 Mo7 O24 }@Ag-MOF provides more active sites, faster ion/electron transfer, and electrolyte diffusion pathways, resulting in excellent specific capacitance (971 F g-1 ) higher than the other compounds. {Ag6 Mo7 O24 }@Ag-MOF (glassy carbon electrode) also has an excellent rate ability (60.1 %) and long cycle stability (98 % retention after 5000 cycles). In addition, the fully symmetrical button battery (with nickel foam as the current collector) fabricated with {Ag6 Mo7 O24 }@Ag-MOF delivers an energy density of 11.1 Wh kg-1 at 600.1 Wh kg-1 coupled with excellent cycling stability (86.4 %) at 1.2 V. These results demonstrate a new simple grinding method to prepare polyoxometalate-based metal-organic frameworks (POMOFs) for high-performance materials.

The Synthesis and Biological Function of a Novel Sandwich-Type Complex Based on {SbW9 } and Flexible bpp Ligand.

A novel sandwich-type complex [Na(H2 O)4 ][{Na3 (H2 O)5 }{Mn3 (bpp)3 } (SbW9 O33 )2 }]·8H3 O (MnSbW-bpp) (bpp = 1,3-bis(4-pyridyl) propane) is synthesized and characterized by elemental analysis, IR, thermogravimetric analysis, and single-crystal X-ray diffraction. The MnSbW-bpp compound is the first sandwich case bridged by a flexible ligand. Its biological function of MnSbW-bpp in antitumor activity is also determined in vitro and in vivo. The inhibitory proliferation and induction of apoptosis are performed by flow cytometry assay, S180 (sarcoma) tumor xenograft in ICR mice, the color Doppler ultrasound monitor, and TdT-mediated dUTP-biotin nick end labeling assay. The results show that the novel compound-MnSbW-bpp-is synthesized and identified by its physical and chemical characteristics, such as the fluorescent and paramagnetic activities. MnSbW-bpp indicates a potency inhibition of human cancer lines, such as SGC-7901, HT-29, HepG2, Hela, U2OS, SaoS2, and HMC cells. MnSbW-bpp also inhibits the growth of tumor xenograft in mice, induced cell apoptosis, and released cytochrome c in vivo and in vitro. Thus, MnSbW-bpp, as a new compound, possesses the potent inhibition of cancer cells, which indicates that the MnSbW-bpp has potential merit for the further evaluation of a novel antitumor agent.

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.

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.

Efficient visible light-driven water oxidation catalysts based on B-ß-{BiW8O30} and unique 14-nuclear hetero-metal sandwich unit.

A sandwich tungstobismuthate with new topology based on {B-ß-BiW8O30}-cluster and unique 14-nuclear sandwich unit is reported as a high-efficiency visible light-driven water oxidation catalyst containing extended hetero-metal oxygen layer. At optimal conditions, the turn-over number (TON) of the title compound can reach 205.5 with O2 yield of 32.88%.

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.

Nonclassical Phosphomolybdates with Different Degrees of Reduction: Syntheses and Structural and Photo/Electrocatalytic Properties.

Four nonclassical phosphomolybdates, formulated as (H2pytty)8[{Mn(H2pytty)(H2O)3}{Sr⊂P6Mo6(V) Mo12(VI)O73}]2·16H2O (1), [{Mn(H3pytty)(H2O)3}2{Sr⊂P6Mo4(V)Mo14(VI)O73}]·18H2O (2), (H3pytp) (H2pytty)2[{Fe(H2O)4}{Sr⊂P6Mo3(V)Mo15(VI)O73}]·5H2O (3), and (H2pytty)2[{Cd(H2O)4}{Cd(H2O)3 (H3pytty)}{Sr⊂P6Mo5(V)Mo13(VI)O73}]·9H2O (4) (pytty = 3-(pyrazin-2-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl; pytp = 4'-(4″-pyridyl)-2,4':6',4″-terpyridine) were hydrothermally synthesized and fully characterized. The penta- and hexa-reduced basket clusters represent the highest reduced level of basket-based polyoxometalate so far. In addition, transition metal complexes as bridge units were introduced to basket system for the first time to induce rare two-dimensional inorganic-organic hybrid layer. The results indicate that reduced degrees of the basket clusters of compounds 1-4 can be tuned by altering the molar ratio of organic ligand pytty and Na2MoO4. Compounds 1-4 exhibit bifunctional electrocatalytic behaviors for oxidation of dopamine and reduction of H2O2. Electrocatalytic mechanism, chronoamperometric experiments and electrocatalytic stability are studied in detail. In addition, the compounds show highly efficient catalytic ability for the degradation of typical 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.

pH and ligand dependent assembly of Well-Dawson arsenomolybdate capped architectures.

Five Well-Dawson-type arsenomolybdates, formulated as [Cu(2,2'-bpy)2][{Cu(2,2'-bpy)}3{As2(V)Mo2(V)Mo16(VI)O62}]·4H2O (1), [H2(4,4'-bpy)]2.5[As(III)(As2(V)Mo2(V)Mo16(VI)O62)]·5H2O (2), (pyr)(imi)(Himi)3[As2(III)(As2(V)Mo3(V)Mo15(VI)O62)]·3H2O (3), [As3(III)(As2(V)Mo3(V)Mo15(VI)O62)]·4H2O (4), and (H2btp)3[As2(V)Mo18(VI)O62]·6H2O (5) (bpy = bipyridine, pyr = pyrazine, imi = imidazole, btp = 1,5-bis(triazol)pentane), have been hydrothermally synthesized and structurally characterized by the elemental analysis, TG, IR, UV-vis-NIR, XPS, XRD, and single-crystal X-ray diffraction. The structural analysis indicates that compounds 1-4 contain rare reduced Dawson {As2Mo18O62} (abbreviated as {As2Mo18}) anions as parent cluster unit, which are capped by a certain number of Cu(II) or As(III) species on different coordination positions via altering pH values and organic ligand of the reaction system. Compounds 1 and 2 are asymmetric tricopper and monoarsenate(III) capped assemble by three {Cu(bpy)}(2+) and a {AsO3} fragments, respectively. Compounds 3 and 4 are symmetric biarsenate(III) and triarsenate(III) capped cluster by four and six half occupancy {AsO3} units, respectively. Compound 5 is uncapped {As2Mo18} structures. Compounds 1-4 represent infrequent Dawson arsenomolybdate capped architectures, especially 2-4, as arsenate(III) capped Dawson-type assemblies are observed for the first time. Compounds 1-5 display good electrocatalytic activity on reduction of nitrite. Compounds 1, 2, 3, and 5 exhibit fluorescent properties in the solid state at room temperature. In addition, magnetic properties of 1-4 have been investigated in detail.