Showing papers on "Polyoxometalate published in 2014"
TL;DR: This study provides not only a valuable molecular model of the "Co-Pi" catalysts with a well-defined structure but also an unprecedented opportunity to fine-tune high-nuclearity POM clusters for visible light-driven water splitting.
Abstract: A series of all-inorganic, abundant-metal-based, high-nuclearity cobalt–phosphate (Co–Pi) molecular catalysts [{Co4(OH)3(PO4)}4(SiW9O34)4]32– (1), [{Co4(OH)3(PO4)}4(GeW9O34)4]32– (2), [{Co4(OH)3(PO4)}4(PW9O34)4]28– (3), and [{Co4(OH)3(PO4)}4(AsW9O34)4]28– (4) were synthesized and shown to be highly effective at photocatalytic water oxidation. The {Co16(PO4)4} cluster contains a Co4O4 cubane which is structurally analogous to the [Mn3CaO4] core of the oxygen-evolving complex (OEC) in photosystem II (PSII). Compounds 1–4 were shown to be the first POM-based Co–Pi-cluster molecular catalysts for visible light-driven water oxidation, thus serving as a functional model of the OEC in PSII. The systematic synthesis of four isostructural analogues allowed for investigating the influence of different heteroatoms in the POM ligands on the photocatalytic activities of these Co–Pi cluster WOCs. Further, the POM-based photocatalysts readily recrystallized from the photocatalytic reaction systems with the polyoxoanion ...
394 citations
TL;DR: Multiple experimental results confirm that the polyanion unit (1-V2) itself is the dominant active catalyst and not Co(2+)(aq) or cobalt oxide.
Abstract: An all-inorganic, oxidatively and thermally stable, homogeneous water oxidation catalyst based on redox-active (vanadate(V)-centered) polyoxometalate ligands, Na10[Co4(H2O)2(VW9O34)2]·35H2O (Na101-V2, sodium salt of the polyanion 1-V2), was synthesized, thoroughly characterized and shown to catalyze water oxidation in dark and visible-light-driven conditions. This synthetic catalyst is exceptionally fast under mild conditions (TOF > 1 × 103 s–1). Under light-driven conditions using [Ru(bpy)3]2+ as a photosensitizer and persulfate as a sacrificial electron acceptor, 1-V2 exhibits higher selectivity for water oxidation versus bpy ligand oxidation, the final O2 yield by 1-V2 is twice as high as that of using [Co4(H2O)2(PW9O34)2]10– (1-P2), and the quantum efficiency of O2 formation at 6.0 μM 1-V2 reaches ∼68%. Multiple experimental results (e.g., UV–vis absorption, FT-IR, 51V NMR, dynamic light scattering, tetra-n-heptylammonium nitrate-toluene extraction, effect of pH, buffer, and buffer concentration, etc....
246 citations
TL;DR: The unique redox property of oxygen-enriched polyoxotungstate fragments and Lewis acidity of the Zr cluster imbedded in Na10K22·1·85H2O provide a sufficient driving force for the catalytic conversion from thioethers to sulfoxides/sulfones.
Abstract: Synergistic directing roles of six lacunary fragments resulted in an unprecedented Zr24-cluster substituted poly(polyoxotungstate) Na10K22[Zr24O22(OH)10(H2O)2(W2O10H)2(GeW9O34)4(GeW8O31)2]·85H2O (Na10K22·1·85H2O), which contains the largest [Zr24O22(OH)10(H2O)2] (Zr24) cluster in all the Zr-based poly(polyoxometalate)s to date. The most remarkable feature is that the centrosymmetric Zr24-cluster-based hexamer contains two symmetry-related [Zr12O11(OH)5(H2O)(W2O10H)(GeW9O34)2(GeW8O31)]16– trimers via six μ3-oxo bridges and was simultaneously trapped by three types of different segments of B-α-GeW9O34, B-α-GeW8O31, and W2O10. The other interesting characteristic is that there are two pairs of intriguing triangular atom alignments: one is composed of the Zr(2,4,6,8,11) and W21 atoms and the other contains the Ge(1–3), Zr(3,5,7,9,10,12) and W26 atoms, and the Zr5 atom is inside the triangle; a linking mode is unobserved. The oxygenation reactions of thioethers by H2O2 were evaluated when Na10K22·1·85H2O serve...
176 citations
TL;DR: By introducing the unprecedented and flexible isomeric bis(pyridyl-tetrazole) ligands into a polyoxometalates (POMs) system, three POM-based compounds were synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction analyses.
Abstract: By introducing the unprecedented and flexible isomeric bis(pyridyl-tetrazole) ligands into a polyoxometalates (POMs) system, three POM-based compounds, {Ag2(4-bptzb)2(H2O)2[H2PMo12O40]2}·4-bptzb·5H2O (1), [Ag4(3-bptzb)2(PMoVMoVI11O40)]·2H2O (2), and Ag3(3-bptzb)2.5(H2O)2[H3P2W18O62] (3) [4-bptzb = 1,4-bis(5-(4-pyridyl)tetrazolyl)butane and 3-bptzb =1,4-bis(5-(3-pyridyl)tetrazolyl)butane], were synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction analyses. Compound 1 exhibits a dimeric structure constructed from two Keggin [PMo12O40]3– anions and a binuclear [Ag2(trans-4-bptzb)2]2+ subunit in which the trans-4-bptzb acts as a bidentate bridging ligand with one tetrazolyl group. In 2, the 3-bptzb acts as a tetradentate bridging ligand with the tetrazolyl and pyridyl groups linking AgI ions to generate a 3D metal–organic framework (MOF), which contains charming meso-helix chains. The Keggin anions acting as bidentate inorganic ligands reside in the dist...
119 citations
TL;DR: General synthetic methods for the grafting of peptide chains onto polyoxometalate clusters by the use of general activated precursors may open the way for the automated synthesis of peptides and perhaps even proteins that contain "inorganic" amino acids.
Abstract: General synthetic methods for the grafting of peptide chains onto polyoxometalate clusters by the use of general activated precursors have been developed. Using a solution-phase approach, pre-synthesized peptides can be grafted to a metal oxide cluster to produce hybrids of unprecedented scale (up to 30 residues). An adapted solid-phase method allows the incorporation of these clusters, which may be regarded as novel hybrid unnatural amino acids, during the peptide synthesis itself. These methods may open the way for the automated synthesis of peptides and perhaps even proteins that contain “inorganic” amino acids.
105 citations
TL;DR: The binding between NCs and oxo ligands strengthens when moving from small oxoanions to polyoxometallates (POMs), and it is shown that small oxoligands and POMs make it possible to tailor NC properties.
Abstract: In this work, we study the functionalization of the nanocrystal (NC) surface with inorganic oxo ligands, which bring a new set of functionalities to all-inorganic colloidal nanomaterials. We show that simple inorganic oxoanions, such as PO43– and MoO42–, exhibit strong binding affinity to the surface of various II–VI and III–V semiconductor and metal oxide NCs. ζ-Potential titration offered a useful tool to differentiate the binding affinities of inorganic ligands toward different NCs. Direct comparison of the binding affinity of oxo and chalcogenidometallate ligands revealed that the former ligands form a stronger bond with oxide NCs (e.g., Fe2O3, ZnO, and TiO2), while the latter prefer binding to metal chalcogenide NCs (e.g., CdSe). The binding between NCs and oxo ligands strengthens when moving from small oxoanions to polyoxometallates (POMs). We also show that small oxo ligands and POMs make it possible to tailor NC properties. For example, we observed improved stability upon Li+-ion intercalation int...
90 citations
TL;DR: Polyoxometalate-functionalized metal-organic frameworks featuring uniform proton-conducting pathways in three orthogonal directions, good water retention and stability were prepared and the proton conductivity of the hybrid material was observed to increase by 5 orders of magnitude.
90 citations
TL;DR: The corrosion resistance against acetic acid vapors and simulated "acid rain" was significantly improved compared with commercial ionic liquids or solid polyoxometalate coatings.
Abstract: Corrosion is a global problem for any metallic structure or material. Herein we show how metals can easily be protected against acid corrosion using hydrophobic polyoxometalate-based ionic liquids (POM-ILs). Copper metal disks were coated with room-temperature POM-ILs composed of transition-metal functionalized Keggin anions [SiW11O39TM(H2O)]n− (TM=CuII, FeIII) and quaternary alkylammonium cations (CnH2 n+1)4N+ (n=7–8). The corrosion resistance against acetic acid vapors and simulated “acid rain” was significantly improved compared with commercial ionic liquids or solid polyoxometalate coatings. Mechanical damage to the POM-IL coating is self-repaired in less than one minute with full retention of the acid protection properties. The coating can easily be removed and recovered by rinsing with organic solvents.
82 citations
TL;DR: This work develops a one-pot strategy for directly converting fructose into 2,5-diformylfuran (DFF) over Mo-containing Keggin heteropolyacids (HPAs) in open air with high activity and selectivity to the formation of DFF owing to its higher Brønsted acidity and moderate redox potential.
Abstract: In this work, a one-pot strategy for directly converting fructose into 2,5-diformylfuran (DFF) over Mo-containing Keggin heteropolyacids (HPAs) in open air is developed. H3 PMo12 O40 HPA is found to show high activity and selectivity to the formation of DFF owing to its higher Bronsted acidity and moderate redox potential. The partial substitution of the H(+) in H3 PMo12 O40 with Cs(+) leads to the heterogenization of the HPA by forming its cesium salts Csx H3-x PMo12 (x=0.5, 1.5, and 2.5). A satisfactory yield of 69.3% to DFF is obtained over Cs0.5 H2.5 PMo12 polyoxometalate after deliberate optimization of the reaction conditions. The heterogenized polyoxometalate could be recycled and reused without significant loss of catalytic activity for five runs. The produced DFF could be separated from the resulting mixture by an adsorption-desorption method using activated carbon as the adsorbent and furfural as the desorbent. A highest isolated yield of 58.2% is obtained.
74 citations
TL;DR: In this paper, the first immobilization of the trivacant Keggin-type polyoxometalate ([A-PW9O34]9−, PW9) to prepare a novel heterogeneous oxidative catalyst is reported.
74 citations
TL;DR: In this article, the authors reported on the assembly of three polyoxometalate-based organic-inorganic hybrid compounds with different helical channels, [Ag3(H2pyttz-I)2][PMo12O40] (1), [Ag6(H 2pyttzi-II)4][CoW12o40]·2H2O (2), and [Ag7(H pyttz)-II)3[GeW12O 40]·7H2
Abstract: Self-assembly of multiple components into well-defined and predictable structures remains one of the foremost challenges in chemistry. Here, upon subtle ligand variation, we reported on the assembly of three new polyoxometalate-based organic–inorganic hybrid compounds with different helical channel, [Ag3(H2pyttz-I)2][PMo12O40] (1), [Ag6(H2pyttz-II)4][CoW12O40]·2H2O (2), and [Ag7(Hpyttz-II)3(H2pyttz-II)][GeW12O40]·7H2O (3) (H2pyttz-I/II = 4-/3-pyrid-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl, POM = polyoxometalates). X-ray diffraction analysis shows that compound 1 is constructed by “butterfly-like” Ag5(H2pyttz-I)2 subunits and POMs clusters, which are assembled into close helical channels impregnated with the components selves. Both compounds 2 and 3 are constructed by “paddle-wheel like” Ag4(H2pyttz-II)4 motifs and POMs clusters, which bring into being the larger helical channels (10.5% and 12.5% of the cell volume, respectively). Note that the only difference in compounds 2 and 3 is that the former conta...
TL;DR: The different coordination modes of POM polyanions and the isomeric bis(pyridylformyl)piperazine ligands play key roles in the construction of the title complexes.
Abstract: Two novel Anderson-type polyoxometalates (POMs)-based metal–organic frameworks (MOFs), namely, H{Cu2(μ2-OH)2L1[CrMo6(OH)6O18]}·4H2O (1), {Cu2L2[CrMoVI5MoV(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 [CrMoVI5MoV(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.
TL;DR: In this paper, the first linear poly(polyoxometalate)s that combine the advantages of polymers and POM clusters were synthesized by linking a Wells-Dawson-type POM with a norbornene derivative.
Abstract: Organic polymers have been found widespread commercial applications due to their easy processing and attractive mechanical properties. Concurrently, inorganic polyoxometalates (POMs), a class of metal–oxygen anionic and nanosized clusters of early transition metals, have a wide range of attractive functions and are used in industrial catalysis. In this communication, we report a new approach to creating the first linear poly(polyoxometalate)s that combine the advantages of polymers and POM clusters. In the experiment, a POM-containing norbornene monomer was first synthesized by linking a Wells-Dawson-type POM with a norbornene derivative. The monomer was polymerized in the presence of a Grubbs catalyst under mild conditions with yields nearly 100% in a living and controllable manner. The resulting poly(polyoxometalate)s have controllable molecular weights and a well-defined hybrid structure of an organic polynorbornene backbone with large pendant groups of the nanosized POM clusters. Thus, they form good ...
TL;DR: The first controlled, stepwise bottom-up assembly route to metal-functionalized molecular vanadium oxides is presented, and cluster stability under technologically relevant conditions in the solid-state and solution is demonstrated.
Abstract: Systematic access to metal-functionalized polyoxometalates has thus far been limited to lacunary tungsten oxide and molybdenum oxide clusters. The first controlled, stepwise bottom-up assembly route to metal-functionalized molecular vanadium oxides is now presented. A di-vacant vanadate cluster with two metal binding sites, (DMA)2[V12O32Cl]3− (DMA=dimethylammonium) is formed spontaneously in solution and characterized by single-crystal X-ray diffraction, ESI mass spectrometry, 51V NMR spectroscopy, and elemental analyses. In the cluster, the metal binding sites are selectively blocked by hydrogen-bonded DMA placeholder cations. Reaction of the cluster with transition metals TM (Fe3+, Co2+, Cu2+, Zn2+) gives access to mono-functionalized vanadate clusters (DMA)[{TM(L)}V12O32Cl]n− (L=ligand). Metal binding is accomplished by significant distortions of the vanadium oxide framework reminiscent of a pincer movement. Cluster stability under technologically relevant conditions in the solid-state and solution is demonstrated.
TL;DR: The combined plasmonic and catalytic effect of Au NPs anchored to the WO3 surface resulted in a large increase of water photooxidation currents and Shielding the Au Nps with polyoxometalates appears to be an effective means to avoid formation of recombination centers at the photoanode surface.
Abstract: Tungsten trioxide (WO3) is one of a few stable semiconductor materials liable to produce solar fuel by photoelectrochemical water splitting. To enhance its visible light conversion efficiency, we incorporated plasmonic gold nanoparticles (Au NPs) derivatized with polyoxometalate (H3PMo12O40) species into WO3. The combined plasmonic and catalytic effect of Au NPs anchored to the WO3 surface resulted in a large increase of water photooxidation currents. Shielding the Au NPs with polyoxometalates appears to be an effective means to avoid formation of recombination centers at the photoanode surface.
TL;DR: XAS reveals the integrity of 1 uncompromised by oxidant-driven water oxidation, which proceeds without formation of catalytic cobalt oxide.
TL;DR: The new material is the first fully inorganic Keggin-type polyoxometalate-based microporous material with intrinsically ordered open micropores and is the third member of the small family of octahedral molecular sieves (OMSs).
Abstract: A new type of polyoxometalate-based porous material was successfully synthesized. The new material is the first fully inorganic Keggin-type polyoxometalate-based microporous material with intrinsically ordered open micropores and is the third member of the small family of octahedral molecular sieves (OMSs). Twelve MoO6 or VO6 octahedra surround a central VO4 tetrahedron to form e-Keggin polyoxometalate building blocks (e-VMo9.4V2.6O40) that are linked by BiIII ions to form crystalline Mo–V–Bi oxide with a diamondoid topology. The presence of a tetrahedral shape of the e-Keggin polyoxometalate building block results in arrangement of microporosity in a tetrahedral fashion which is new in OMSs. Owing to its microporosity, this Mo–V–Bi oxide shows zeolitic-like properties such as ion-exchange and molecule adsorption.
TL;DR: A novel polyoxometalate-based metal organic framework (POMOF) constructed from isolated isopolyoxotungstate, which acted as a Lewis acid catalyst through a heterogeneous manner to prompt cyanosilylation with excellent efficiency.
Abstract: A novel polyoxometalate-based metal organic framework (POMOF) constructed from isolated isopolyoxotungstate [H2W11O38]8– cluster, {[Cu2(bpy)(H2O)5.5]2[H2W11O38]·3H2O·0.5CH3CN} (1, where bpy = 4,4′-bpydine), has been synthesized under solvothermal conditions and charaterized by elemental analysis, infrared spectroscopy, and single-crystal X-ray diffraction. In 1, {W11} clusters are alternately linked by two [Cu(2)(H2O)1.5(Ot)3(N)]2+ cations in an unexpected end-to-end fashion leading to a one-dimensional (1D) chain. Adjacent 1D chains are linked through Cu(1)–bpy–Cu(2) in an opposite direction to form a two-dimensional (2D) wavelike sheet along the ab plane. These 2D sheets are further stacked in a parallel fashion giving rise to the 1D channels with copper(II) cations aligned in the channels. The resulting POMOF acted as a Lewis acid catalyst through a heterogeneous manner to prompt cyanosilylation with excellent efficiency.
TL;DR: Initial investigations into the ability of the Ru4POM LBL films to electrocatalytically oxidise water at pH 7 have also been conducted.
Abstract: A tetra Ru-substituted polyoxometalate Na10[{Ru4O4(OH)2(H2O)4}(γ-SiW10O36)2] (Ru4POM) has been successfully immobilised onto glassy carbon electrodes and indium tin oxide (ITO) coated glass slides through the employment of a conducting polypyrrole matrix and the layer-by-layer (LBL) technique. The resulting Ru4POM doped polypyrrole films showed stable redox behavior associated with the Ru centres within the Ru4POM, whereas, the POM’s tungsten-oxo redox centres were not accessible. The films showed pH dependent redox behavior within the pH range 2–5 whilst exhibiting excellent stability towards redox cycling. The layer-by-layer assembly was constructed onto poly(diallyldimethylammonium chloride) (PDDA) modified carbon electrodes by alternate depositions of Ru4POM and a Ru(II) metallodendrimer. The resulting Ru4POM assemblies showed stable redox behavior for the redox processes associated with Ru4POM in the pH range 2–5. The charge transfer resistance of the LBL films was calculated through AC-Impedance. Su...
TL;DR: Four 3D POM-based silver coordination polymers, namely, Ag17(ptz)11(PW12O40)2]n (1), [Ag17(PTz) 11(PMo12O 40)2[n (2], [Ag12(ptZ)6(CN)2(SiW 12O40)]n (3), and [Ag19(pttz)8(H2ptz)(H3ptz),
Abstract: Four 3D POM-based silver coordination polymers, namely, [Ag17(ptz)11(PW12O40)2]n (1), [Ag17(ptz)11(PMo12O40)2]n (2), [Ag12(ptz)6(CN)2(SiW12O40)]n (3), and [Ag19(ptz)8(H2ptz)(H3ptz)(AgP5W30O110)·7H2O]n (4), have been obtained by solvothermal reaction of AgNO3 and 5-phenyl-1H-tetrazole (Hptz) ligand in the presence of four types of polyoxometalates. Structural analysis shows that four types of Ag(I)···π interactions, m-η1, m/p-η2, o/m-η2, and o/m/p-η3, were observed in compounds 1–4, depending on the polyoxometalates used. The in situ generated CN– ion in compound 3 shows unprecedented mixed σ and π bonding modes, similar to the C22- ion in well-studied silver acetylides. For 4, the Na+ ion in the Preyssler heteropolyoxoanion, [NaP5W30O110]14-, was exchanged by Ag(I) under solvothermal conditions, generating a novel [AgP5W30O110]14- anion. In addition, the photoluminescence behavior of 1–4 was also investigated.
TL;DR: A three-component supramolecular hybrid system based on host-guest recognition and electrostatic interaction has been developed for a consecutive chiral transfer from an alpha-cyclodextrin to cationic dyes via the bridge of a new azobenzene-grafted Anderson-type polyoxometalate cluster.
TL;DR: In this article, a family of benign polyoxometalate-based ionic liquid salts (POM-ILs) was designed and prepared by combining Keggin-structured polyoxometricalate inorganic anions with sulfonate functionalized organic cations.
TL;DR: In this paper, the primary Keggin structure remains after incorporation in amorphous silica matrix, and the synthesized PWFe/SiO2 composite showed an elevated catalytic activity and selectivity with high to excellent yields for oxidation of alcohols into aldehydes by H2O2.
Abstract: Fe(III) substituted Keggin type polyoxometalate in amorphous silica matrix, (n-C4H9)4N)4[PW11FeO39]/SiO2 (PWFe/SiO2), has been synthesized by sol–gel method. The synthesized PWFe/SiO2 composite was characterized by various analytical and spectroscopic techniques. Results indicated that the primary Keggin structure remain after incorporation in silica matrix. As a heterogeneous catalyst, PWFe/SiO2 composite showed an elevated catalytic activity and selectivity with high to excellent yields for oxidation of alcohols into aldehydes by H2O2. The stability and reusability of the catalyst was very high, so these composites are suitable for the heterogeneous catalysis by hydrogen peroxide.
TL;DR: The synthesis of well-ordered porous polyoxometalate-Ag2S-CdS hybrid mesostructures featuring a controllable composition and high photocatalytic activity via a two-step hard-templating and topotactic ion-exchange chemical process is reported.
Abstract: Porous multicomponent semiconductor materials show improved photocatalytic performance due to the large and accessible pore surface area and high charge separation efficiency. Here we report the synthesis of well-ordered porous polyoxometalate (POM)–Ag2S–CdS hybrid mesostructures featuring a controllable composition and high photocatalytic activity via a two-step hard-templating and topotactic ion-exchange chemical process. Ag2S compounds and polyoxometalate cluster anions with different reduction potentials, such as PW12O403−, SiW12O404− and PMo12O403−, were employed as electron acceptors in these ternary heterojunction photocatalysts. Characterization by small-angle X-ray scattering, X-ray diffraction, transmission electron microscopy and N2 physisorption measurements showed hexagonal arrays of POM–Ag2S–CdS hybrid nanorods with large internal BET surface areas and uniform mesopores. The Keggin structure of the incorporated POM clusters was also verified by elemental X-ray spectroscopy microanalysis, infrared and diffuse-reflectance ultraviolet-visible spectroscopy. These new porous materials were implemented as visible-light-driven photocatalysts, displaying exceptional high activity in aerobic oxidation of various para-substituted benzyl alcohols to the corresponding carbonyl compounds. Our experiments show that the spatial separation of photogenerated electrons and holes at CdS through the potential gradient along the CdS–Ag2S–POM interfaces is responsible for the increased photocatalytic activity.
TL;DR: In this article, a reversible phase transformation-type electrolyte, consisting of 1-(3-sulfonic group)propyl-3-methyl imidazolium cation (MIMPS) and tungstovanadophosphoric anion with Keggin structure, was synthesized and characterized using elemental analysis, IR, UV, XRD and TG-DTA.
Abstract: Reversible phase transformation-type electrolyte, consisting of 1-(3-sulfonic group)propyl-3-methyl imidazolium cation (MIMPS) and tungstovanadophosphoric anion with Keggin structure, [MIMPS]4PW11VO40, is synthesized and characterized using elemental analysis, IR, UV, XRD, and TG-DTA. This product is in quasi-solid-state, a novel type of ionic liquid, with a layered type of structure. This compound can process the phase transition from a crystal phase to an isotropic phase below 100 °C. Moreover, the DTA and conductivity–temperature plot shows an observable increase in conductivity above 84.2 °C, which is caused by the phase transformation from crystal phase to isotropic phase. This novel electrolyte material exhibits high conductivity (8.60 × 10−2 S cm−1 at 83 °C and 80% relative humidity). In the range of the measured temperature, its conductivity increases with higher temperature, indicating that the conductive activation energy for this conduction step is 42.06 kJ mol−1.
TL;DR: Tetramer 3 comprises bridging Sn(II) ions with [B-SbW9O33](9-) units and exhibits two highly unusual features, a long-range Sb···Sb interaction and an intramolecular charge-transfer transition involving donation of the lone-pair electron density on both Sb(III) and Sn( II) to the POM.
Abstract: Two MOF-like but all-inorganic polyoxometalate-based networks, [Na7X2W18Sn9Cl5O68·(H2O)m]n (1, X = Si, m = 35; 2, X = Ge, m = 41), and the molecular tetramer Na6[{Na(μ-OH2)(OH2)2}6{Sn6(B-SbW9O33)2}2]·50H2O (3) have been prepared and characterized by X-ray diffraction and spectroscopic methods. All three compounds exhibit unique structural features, and networks 1 and 2 incorporate the highest nuclearity of Sn(II)-containing POMs to date. Tetramer 3 comprises bridging Sn(II) ions with [B-SbW9O33]9– units and exhibits two highly unusual features, a long-range Sb···Sb interaction and an intramolecular charge-transfer transition involving donation of the lone-pair electron density on both Sb(III) and Sn(II) to the POM. The electronic structure and excited-state dynamics have been studied by transient spectroscopy, spectroelectrochemistry, DFT calculations, and resonance Raman spectroscopy. The synergistic effect of two types of stereoactive lone-pairs on Sb(III) and Sn(II) is critical for the charge-transfer ...
TL;DR: A novel organometallic-polyoxometalate hybrid has been prepared by anion-exchange of V Schiff base functionalized ionic liquid with V-containing Keggin-type polyoxmetalate.
TL;DR: Mechanistic interpretations of methanol dehydration turnover rates are used to assess how charge reorganization (covalency) and electrostatic interactions determine DPE and how such interactions are recovered when intermediates and transition states interact with the conjugate anion in W and Mo polyoxometalate clusters and gaseous mineral acids.
Abstract: Reactivity descriptors describe catalyst properties that determine the stability of kinetically relevant transition states and adsorbed intermediates. Theoretical descriptors, such as deprotonation energies (DPE), rigorously account for Bronsted acid strength for catalytic solids with known structure. Here, mechanistic interpretations of methanol dehydration turnover rates are used to assess how charge reorganization (covalency) and electrostatic interactions determine DPE and how such interactions are recovered when intermediates and transition states interact with the conjugate anion in W and Mo polyoxometalate (POM) clusters and gaseous mineral acids. Turnover rates are lower and kinetically relevant species are less stable on Mo than W POM clusters with similar acid strength, and such species are more stable on mineral acids than that predicted from W-POM DPE–reactivity trends, indicating that DPE and acid strength are essential but incomplete reactivity descriptors. Born–Haber thermochemical cycles i...
TL;DR: In this article, a molecular Keggin polyoxometalate catalyst was successfully synthesized and efficiently catalyzed the hydrogen evolution under the visible light irradiation condition, which achieved 13,395μmol h −1 ǫg −1 −1, which is the highest among all the polyoxmetalates photocatalytic systems reported so far.
TL;DR: Two extended Preyssler P5W30 polyoxometalate-based inorganic-organic hybrid materials exhibiting anion-induced supramolecular isomerism were reported and show electrocatalytic abilities on the reduction of H2O2.
Abstract: Two extended Preyssler P5W30 polyoxometalate-based inorganic-organic hybrid materials exhibiting anion-induced supramolecular isomerism were reported. Because of the cis-trans isomerism in the octahedral CoN2O4 coordination geometry, the Preyssler P5W30 polyoxometalates are extended by double O-Co-O bridges in 1α and a single O-Co-O bridge in 1β to form the isomeric 2D 4-connected 4(4)-sql and 3D 8-connected bcu networks, respectively. Both compounds show electrocatalytic abilities on the reduction of H2O2.