Showing papers on "Polyoxometalate published in 2015"
TL;DR: As a 3D hydrogen-evolving cathode operating in acidic electrolytes, NENU-500 exhibits the highest activity among all MOF materials and maintains their electrocatalytic activities after 2000 cycles.
Abstract: Two novel polyoxometalate (POM)-based metal–organic frameworks (MOFs), [TBA]3[e-PMoV8MoVI4O36(OH)4Zn4][BTB]4/3·xGuest (NENU-500, BTB = benzene tribenzoate, TBA+ = tetrabutylammonium ion) and [TBA]3[e-PMoV8MoVI4O37(OH)3Zn4][BPT] (NENU-501, BPT = [1,1′-biphenyl]-3,4′,5-tricarboxylate), were isolated. In these compounds, the POM fragments serving as nodes were directly connected with organic ligands giving rise to three-dimensional (3D) open frameworks. The two anionic frameworks were balanced by TBA+ ions residing inside the open channels. They exhibit not only good stability in air but also tolerance to acidic and basic media. Furthermore, they were employed as electrocatalysts for the hydrogen evolution reaction (HER) owing to the combination of the redox activity of a POM unit and the porosity of a MOF. Meanwhile, the HER activities of e(trim)4/3, NENU-5, and HKUST-1 were also studied for comparison. Remarkably, as a 3D hydrogen-evolving cathode operating in acidic electrolytes, NENU-500 exhibits the hig...
518 citations
TL;DR: MoO2 @PC-RGO hybrid material derived from the POMOFs/GO composite is prepared at a relatively low carbonization temperature, which presents a superior activity for the hydrogen-evolution reaction (HER) in acidic media owing to the synergistic effects among highly dispersive MoO2 particles, phosphorus-doped porous carbon, and RGO substrates.
Abstract: We have synthesized a porous Mo-based composite obtained from a polyoxometalate-based metal–organic framework and graphene oxide (POMOFs/GO) using a simple one-pot method. The MoO2@PC-RGO hybrid material derived from the POMOFs/GO composite is prepared at a relatively low carbonization temperature, which presents a superior activity for the hydrogen-evolution reaction (HER) in acidic media owing to the synergistic effects among highly dispersive MoO2 particles, phosphorus-doped porous carbon, and RGO substrates. MoO2@PC-RGO exhibits a very positive onset potential close to that of 20 % Pt/C, low Tafel slope of 41 mV dec−1, high exchange current density of 4.8×10−4 A cm−2, and remarkable long-term cycle stability. It is one of the best high-performance catalysts among the reported nonprecious metal catalysts for HER to date.
381 citations
TL;DR: Hierarchical organization of photosensitizing and catalytic proton reduction components in such a POM@MOF assembly enables fast multielectron injection from the photoactive framework to the encapsulated redox-active POMs upon photoexcitation, leading to efficient visible-light-driven hydrogen production.
Abstract: A simple and effective charge-assisted self-assembly process was developed to encapsulate a noble-metal-free polyoxometalate (POM) inside a porous and phosphorescent metal–organic framework (MOF) built from [Ru(bpy)3]2+-derived dicarboxylate ligands and Zr6(μ3-O)4(μ3-OH)4 secondary building units. Hierarchical organization of photosensitizing and catalytic proton reduction components in such a POM@MOF assembly enables fast multielectron injection from the photoactive framework to the encapsulated redox-active POMs upon photoexcitation, leading to efficient visible-light-driven hydrogen production. Such a modular and tunable synthetic strategy should be applicable to the design of other multifunctional MOF materials with potential in many applications.
335 citations
TL;DR: Multiple experiments including dynamic light-scattering, UV-vis absorption, catalysts aged experiments, tetra-n-heptylammonium nitrate extraction, and capillary electrophoretic measurements results confirm that compounds 1-3 are dominant active catalysts but not Ni(2+) ions(aq), nickel oxide under the photocatalytic conditions.
Abstract: Three new polyoxometalate(POM)-based polynuclear nickel clusters, Na24[Ni12(OH)9(CO3)3(PO4)(SiW9O34)3]·56H2O (1), Na25[Ni13(H2O)3(OH)9(PO4)4(SiW9O34)3]·50H2O (2), and Na50[Ni25(H2O)2OH)18(CO3)2(PO4)6(SiW9O34)6]·85H2O (3) were synthesized and structurally characterized. Compounds 1-3 contain {Ni12}, {Ni13} and {Ni25} core, respectively, connected by the inorganic {OH}, {PO4} and/or {CO3} linkers and encapsulated by the lacunary A-α-{SiW9O34} POM units. Compound 3 represents the currently largest POM-based Ni clusters. All three compounds contain {Ni3O3} quasi-cubane or {Ni4O4} cubane units, which are similar to the natural oxygen-evolving center {Mn4O5Ca} in photosystem II (PSII). Visible light-driven water oxidation experiments with compounds 1-3 as the homogeneous catalysts indicate that all three compounds show good photocatalytic activities. The O2 evolution amount corresponds to a high TON of 128.2 for 1, 147.6 for 2, and 204.5 for 3, respectively. Multiple experiments including dynamic light-scattering, UV-vis absorption, catalysts aged experiments, tetra-n-heptylammonium nitrate (THpANO3) toluene extraction, and capillary electrophoretic measurements results confirm that compounds 1-3 are dominant active catalysts but not Ni(2+) ions(aq) or nickel oxide under the photocatalytic conditions. The above research results indicate a new and all-inorganic polynuclear Ni-based structural model as the visible light-driven water oxidation catalysts.
314 citations
TL;DR: By incorporating a pyrrolidine moiety as a chiral organocatalyst and a polyoxometalate as an oxidation catalyst, a powerful approach is devised to achieve a tandem catalyst for the efficient conversion of CO2 into value-added enantiomerically pure cyclic carbonates.
Abstract: Currently, great interest is focused on developing auto-tandem catalytic reactions; a substrate is catalytically transferred through mechanistically distinct reactions without altering any reaction conditions. Here by incorporating a pyrrolidine moiety as a chiral organocatalyst and a polyoxometalate as an oxidation catalyst, a powerful approach is devised to achieve a tandem catalyst for the efficient conversion of CO2 into value-added enantiomerically pure cyclic carbonates. The multi-catalytic sites are orderly distributed and spatially matched in the framework. The captured CO2 molecules are synergistically fixed and activated by well-positioned pyrrolidine and amine groups, providing further compatibility with the terminal W=O activated epoxidation intermediate and driving the tandem catalytic process in a single workup stage and an asymmetric fashion. The structural simplicity of the building blocks and the use of inexpensive and readily available chemical reagents render this approach highly promising for the development of practical homochiral materials for CO2 conversion.
212 citations
TL;DR: In this paper, Mehmet Lutfi Yola et al. determined triclosan based on gold nanoparticles on polyoxometalate/reduced graphene oxide nanohybrid.
Abstract: Correction for ‘Sensitive and selective determination of aqueous triclosan based on gold nanoparticles on polyoxometalate/reduced graphene oxide nanohybrid’ by Mehmet Lutfi Yola et al., RSC Adv., 2015, 5, 65953–65962.
166 citations
TL;DR: Modulating the facets of a crystalline MOF NENU-3a is presented to enhance the facet exposure of the catalytic sites and the adsorption of substrates to achieve enhanced catalysis for sterically demanding substrates that are otherwise hard to diffuse into the pores.
Abstract: An inherent challenge in using metal–organic frameworks (MOFs) for catalysis is how to access the catalytic sites generally confined inside the porous structure, in particular for substrates larger than the pores. We present here a promising solution to bypass this roadblock by modulating the facets of a crystalline MOF NENU-3a to enhance the facet exposure of the catalytic sites and the adsorption of substrates. Specifically, by transforming it with encapsulated catalysis-responsible polyoxometalate from octahedron characterized entirely by {111} facets to cube with only {100} facets, much enhanced catalytic activities were observed, especially for sterically demanding substrates that are otherwise hard to diffuse into the pores. Crystallographic analysis and adsorption/desorption experiments collectively established the critical effects of morphological control on the enhanced catalysis. The cubic crystals were then applied for biodiesel production, reaching more than 90% conversion of fatty acids (C12–...
143 citations
TL;DR: This hybrid contains the largest number of 4f ions of any polyoxometalate (POM) reported to date and is the first to incorporate two different 3d-4f and 4f coordination cluster assemblies within same POM framework.
Abstract: A giant tetrahedral heterometallic polyoxometalate (POM) [Dy30Co8Ge12W108O408(OH)42(OH2)30]56−, which shows single-molecule magnet (SMM) behavior, is described This hybrid contains the largest number of 4f ions of any polyoxometalate (POM) reported to date and is the first to incorporate two different 3d–4f and 4f coordination cluster assemblies within same POM framework
129 citations
TL;DR: In this paper, a composite material comprising the chromium terephthalate metal-organic framework MIL-101 and the tetrabutylammonium (TBA) salt of a zinc-substituted polyoxotungstate anion, TBA 4.2 H 0.8 [PW 11 Zn(H 2 O)O 39 ] (denoted PW11 Zn), has been prepared by an impregnation method and characterized by powder X-ray diffraction, scanning electron microscopy, N 2 adsorption/desorption
123 citations
TL;DR: A large improvement in the operational characteristics of organic light emitting devices and organic photovoltaics based on a wide range of different organic semiconducting materials and incorporating reduced Pom/Al cathode interfaces was achieved as a result of the large decrease of the electron injection/extraction barrier, the enhanced electron transport and the reduced recombination losses in the reduced POM modified devices.
Abstract: The present study is aimed at investigating the solid state reduction of a representative series of Keggin and Dawson polyoxometalate (POM) films in contact with a metallic (aluminum) electrode and at introducing them as highly efficient cathode interlayers in organic optoelectronics. We show that, upon reduction, up to four electrons are transferred from the metallic electrode to the POM clusters of the Keggin series dependent on addenda substitution, whereas a six electron reduction was observed in the case of the Dawson type clusters. The high degree of their reduction by Al was found to be of vital importance in obtaining effective electron transport through the cathode interface. A large improvement in the operational characteristics of organic light emitting devices and organic photovoltaics based on a wide range of different organic semiconducting materials and incorporating reduced POM/Al cathode interfaces was achieved as a result of the large decrease of the electron injection/extraction barrier...
106 citations
TL;DR: The catalytic activity of compound 1 in the oxidative desulfurization reaction indicates that it is not only an effective and size-selective heterogeneous catalyst, but it also exhibits distinct structural stability in the catalytic reaction system.
Abstract: A new cationic triazole-based metal-organic framework encapsulating Keggin-type polyoxometalates, with the molecular formula [Co(BBPTZ)3][HPMo12O40]⋅24 H2O [compound 1; BBPTZ = 4,4'-bis(1,2,4-triazol-1-ylmethyl)biphenyl] is hydrothermally synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, powder X-ray diffraction, and single-crystal X-ray diffraction. The structure of compound 1 contains a non-interpenetrated 3D CdSO4 (cds)-type framework with two types of channels that are interconnected with each other; straight channels that are occupied by the Keggin-type POM anions, and wavelike channels that contain lattice water molecules. The catalytic activity of compound 1 in the oxidative desulfurization reaction indicates that it is not only an effective and size-selective heterogeneous catalyst, but it also exhibits distinct structural stability in the catalytic reaction system.
TL;DR: An eleven iron-containing nanoscale inorganic polyanionic oxide cluster was reported as the first example for exceptional photocatalytic water oxidation.
TL;DR: The use of 1H-1,2,4-triazole-3-thiol (H2trzS) has led to a rare inorganic-organic hybrid supramolecular nanotube built from novel Ni5-substituted polyoxotungstates, which presents interesting structural characteristics, high chemical stability, and proton-conducting properties.
TL;DR: It is reported for the first time polyoxometalate (POM)-based single-molecule magnets with mononuclear transition metal cores with Mononuclear paramagnetic metal ions under the applied dc field.
TL;DR: A stable metal-organic framework pillared by Keggin-type polyoxometalate showed efficient intrinsic peroxidase-like activity, providing a simple and sensitive colorimetric assay to detect H2O2.
Abstract: A stable metal-organic framework pillared by Keggin-type polyoxometalate, Cu6 (Trz)10 (H2O)4 [H2 SiW12 O40 ]⋅8 H2O (Trz=1,2,4-triazole) (1), has been prepared under hydrothermal condition. The 2D layer structure with a 22-member ring was formed by Cu(2+) ions, which are connected with each other via the Trz ligands on the ab plane. Thus, the 2D layers are further interconnected through Keggin polyoxoanions to generate a 3D porous network with a small 1D channel. Moreover, the presence of polyoxoanions make it exhibit selective adsorption of water and proton-conducting properties. Additionally it showed efficient intrinsic peroxidase-like activity, providing a simple and sensitive colorimetric assay to detect H2O2 .
TL;DR: Electrochemical analyses show that the nanocomposite displays improved performance as an anode material in lithium ion batteries compared with the individual components, that is, SWNTs and/or Anderson clusters.
Abstract: Single-walled carbon nanotubes (SWNTs) covalently functionalized with redox-active organo-modified polyoxometalate (POM) clusters have been synthesized and employed as electrode materials in lithium ion batteries. The Anderson cluster [MnMo6O24]9− is functionalized with Tris (NH2C(CH2OH)3) moieties, giving the new organic–inorganic hybrid [N(nC4H9)4]3[MnMo6O18{(OCH2)3CNH2}2]. The compound is then covalently attached to carboxylic acid-functionalized SWNTs by amide bond formation and the stability of this nanocomposite is confirmed by various spectroscopic methods. Electrochemical analyses show that the nanocomposite displays improved performance as an anode material in lithium ion batteries compared with the individual components, that is, SWNTs and/or Anderson clusters. High discharge capacities of up to 932 mAh g−1 at a current density of 0.5 mA cm−2 can be observed, together with high long-term cycling stability and decreased electrochemical impedance. Chemisorption of the POM cluster on the SWNTs is shown to give better electrode performance than the purely physisorbed analogues.
TL;DR: Investigation by several spectroscopy, spectrometry, and other techniques confirm that Co8POM is a stable and efficient catalyst for visible light-driven water oxidation.
Abstract: To overcome the bottleneck of water splitting, the exploration of efficient, selective, and stable water oxidation catalysts (WOCs) is crucial. We report an all-inorganic, oxidatively and hydrolytically stable WOC based on a polyoxometalate [(A- -SiW 9 O 34 ) 2 Co 8 (OH) 6 (H 2 O) 2 (CO 3 ) 3 ] 16− (Co 8 POM). As a cobalt(II)-based cubane water oxidation catalyst, Co 8 POM embeds double Co II 4 O 3 cores. The self-assembled catalyst is similar to the oxygen evolving complex (OEC) of photosystem II (PS II). Using [Ru(bpy) 3 ] 2+ as a photosensitizer and persulfate as a sacrificial electron acceptor, Co 8 POM exhibits excellent water oxidation activity with a turnover number (TON) of 1436, currently the highest among bioinspired catalysts with a cubical core, and a high initial turnover frequency (TOF). Investigation by several spectroscopy, spectrometry, and other techniques confirm that Co 8 POM is a stable and efficient catalyst for visible light-driven water oxidation. The results offer a useful insight into the design of water oxidation catalysts.
TL;DR: This review summarizes the design and synthesis of organic–inorganic hybrid POM compounds and particularly highlights their recent progress in heterogeneous catalysis.
Abstract: Organic-inorganic hybrid polyoxometalate (POM) compounds are a subset of materials with unique structures and physical/chemical properties. The combination of metal-organic coordination complexes with classical POMs not only provides a powerful way to gain multifarious new compounds but also affords a new method to modify and functionalize POMs. In parallel with the many reports on the synthesis and structure of new hybrid POM compounds, the application of these compounds for heterogeneous catalysis has also attracted considerable attention. The hybrid POM compounds show noteworthy catalytic performance in acid, oxidation, and even in asymmetric catalytic reactions. This review summarizes the design and synthesis of organic-inorganic hybrid POM compounds and particularly highlights their recent progress in heterogeneous catalysis.
TL;DR: The first polyoxometalate-based metal-organic nanotube constructed via covalent bonds has been synthesized and the stability, magnetic and proton conducting properties are investigated.
TL;DR: A series of polyoxometalate (POM)-based metal-organic complexes containing multinuclear Cu(II) clusters with a 4-amino-1,2,4-triazole (4-atrz) ligand have been synthesized by selectively adding additional citric acid or boric acid under hydrothermal conditions as mentioned in this paper.
Abstract: A series of polyoxometalate (POM)-based metal–organic complexes containing multinuclear Cu(II) clusters with a 4-amino-1,2,4-triazole (4-atrz) ligand, namely, [Cu3(4-atrz)8(PMo12O40)2(H2O)2]·2H2O (1), [Cu2(4-atrz)6(SiW12O40)(H2O)]·6H2O (2), [Cu2(4-atrz)4(μ2-OH)(CrMo6(OH)6O18)]·3H2O (3), [Cu3(4-atrz)3(Mo8O27)(H2O)4]·6H2O (4) and [Cu3(4-atrz)3(V10O30)0.5(μ3-OH)(H2O)]·H2O (5) have been synthesized by selectively adding additional citric acid or boric acid under hydrothermal conditions and have been structurally characterized by single-crystal X-ray diffraction and powder X-ray diffraction. Compound 1 has a zero-dimensional (0D) architecture, which is constructed from a linear trinuclear cluster [Cu3(4-atrz)8(H2O)2]6+ and two Keggin PMo12O403− anions. Compound 2 shows a 1D zigzag chain, in which the binuclear [Cu2(4-atrz)6(H2O)]4+ clusters and Keggin SiW12O404− anions connect to each other. Compound 3 is a 1D linear chain based on linear [Cu3(4-atrz)6]6+ clusters; the [CrMo6(OH)6O18]3− anions hang on two sides of the 1D chain. Compound 4 has a 2D layer constructed from trigonal [Cu3(4-atrz)3(H2O)4]6+ clusters and rare infinite [Mo8O27]n6n− chains. The [Mo8O27]6− anion is transformed from the Anderson-type [CoMo6(OH)6O18]3− anion, which is also rare in the POM-based reaction system. Compound 5 has a 3D framework constructed from trigonal trinuclear [Cu3(4-atrz)3(OH)]5+ clusters and rare [V10O30]10− polyanions, which represents the first example of a V10O30-based 3D metal–organic complex. Structural analyses indicate that different POMs show great effect on the various structures of 1–5 and the additional acids play an important role in the formation of 1–5. Photocatalytic experiments of 1–5 on degradation of three organic dyes (methylene blue, Rhodamine B and methyl orange) manifest that compounds 1–3 are good candidates for the photocatalytic degradation of methylene blue, and compound 1 is a good photocatalyst for the degradation of Rhodamine B.
TL;DR: A new type of supramolecular chemosensor based on a polyoxometalate and a block copolymer was constructed for the qualitative and quantitative detection of CO2.
Abstract: A new type of supramolecular chemosensor based on the polyoxometalate (POM) Na9DyW10O36 (DyW10) and the block copolymer poly(ethylene oxide-b-N,N-dimethylaminoethyl methacrylate) (PEO114-b-PDMAEMA16) is reported. By taking advantage of the CO2 sensitivity of PDMAEMA blocks to protonate the neutral tertiary amino groups, CO2 can induce the electrostatic coassembly of anionic DyW10 with protonated PDMAEMA blocks, and consequently trigger the luminescence chromism of DyW10 due to the change in the microenvironment of Dy3+. The hybrid complex in dilute aqueous solution is very sensitive to CO2 content and shows rapid responsiveness in luminescence. The luminescence intensity of the DyW10/PEO-b-PDMAEMA complex increases linearly with an increasing amount of dissolved CO2, which permits the qualitative and quantitative detection of CO2. The complex solution also shows good selectivity for CO2, with good interference tolerance of CO, N2, HCl, H2O and SO2. The supramolecular chemosensor can be recycled through disassembly of the hybrid complex by simply purging with inert gases to remove CO2.
TL;DR: In this article, an amphiphilic polyoxometalate-based supported silica [C 4 mim] 3 PW 12 O 40 /SiO 2 was successfully synthesized by a facile hydrothermal process and employed in ODS process.
Abstract: As strict regulations of fuel specifications implemented, oxidative desulfurization process (ODS) is considered as one of the promising technologies to achieve deep desulfurization under mild conditions. Herein, amphiphilic polyoxometalate-based supported silica [C 4 mim] 3 PW 12 O 40 /SiO 2 was successfully synthesized by a facile hydrothermal process and employed in ODS process. The composition and structure of obtained hybrid samples were characterized by means of FT-IR, XPS, Raman, 31 P MAS NMR, UV–vis, wide-angle XRD, N 2 adsorption–desorption and SEM. The experimental results indicated that the as-synthesized materials maintained the integrity of architecture of polyoxometalate-based ionic liquids (POM-based ILs), which were finely dispersed into the silica matrix. Besides, the sample [C 4 mim] 3 PW 12 O 40 /SiO 2 possessed moderate hydrophilic–hydrophobic balanced surface leading to higher sulfur removal. Moreover, the effects of the amount of catalyst, H 2 O 2 /DBT molar ratio, temperature, types of sulfur-containing substrate on the sulfur removal were also investigated in detail. Under optimal conditions, dibenzothiophene (DBT) could be completely removed in 30 min.
TL;DR: A combination of a Keggin-type polyoxometalate (POM), with a Cu3(BTC)2 metal-organic framework (MOF-199/HKUST-1), was successfully self-assembled on a cellulose substrate (cotton) with a room-temperature process.
Abstract: A combination of a Keggin-type polyoxometalate (POM), [CuPW11O39]5–, with a Cu3(BTC)2 metal–organic framework (MOF-199/HKUST-1; where BTC is benzene-1,3,5-tricarboxylate), was successfully self-assembled on a cellulose substrate (cotton) with a room-temperature process. Cotton fibers were functionalized by partial etherification. Cu3(BTC)2 metal–organic framework and polyoxometalate encapsulated in Cu3(BTC)2 metal–organic framework were self-assembled on the carboxymethylate ion sites initiated with copper nitrate using ethanol and water as solvents. Octahedral crystals were observed on both MOF-cotton and POM-MOF-cotton; both contained copper while the POM-MOF-cotton also contained tungsten. Occupancy of POM in MOF cages was calculated to be about 13%. Moisture content remained at 3 to 4 wt % similar to that of untreated cotton. Reactivity to both hydrogen sulfide and methyl parathion was higher for POM-MOF-cotton due to the Keggin polyoxometalate and the extra-framework cations Cu2+ ions compensating th...
TL;DR: In this paper, the Keggin-type polyoxometalate (POM) anions were introduced into metal-organic frameworks (MOF) precursors, and various uniform [Cu3(BTC)2] n (BTC = benzene-1,3,5-tricarboxylate) NCs, including (truncated) octahedrons, hollow hierarchical spheres and octahedral structures, were fabricated.
Abstract: Host-guest supramolecular interactions, which exist widely between diverse metal cations and polyoxometalate (POM) anions, have always been utilized to construct metal-organic frameworks (MOF) /POMs bulk composites Actually, the interactions can also be found application in realizing shape-controlled synthesis of MOF nanocrystals (NCs) In this context, simply by introducing Keggin-type POMs into MOF precursors, various uniform [Cu3(BTC)2] n (BTC = benzene-1,3,5-tricarboxylate) NCs, including (truncated) octahedrons, hollow hierarchical spheres and octahedrons, are fabricated Besides, such reaction system can be applied to construct noble metal@MOF nanocomposite, which significantly enhances the catalytic performance of the noble metal
TL;DR: Variable-temperature magnetic susceptibility studies revealed that an antiferromagnetic interaction exists within the Cu20 nanocluster, and the correlation between the coordination structure and the electron paramagnetic resonance spectra recorded of both powder and single-crystal samples are discussed.
Abstract: The encapsulation of carbonate derived from atmospheric CO2 has resulted in an icosanuclear heteropolyoxocopperate, isolated as a metal-organic 1D chain, 2D sheet, or 3D framework, in which the Cu20 nanocluster represents the first eight-capped α-Keggin polyoxometalate with the late-transition-metal Cu(II) as the polyatom, CO3(2-) as the heteroanion, and OH(-) and suc(2-) or glu(2-) (H2suc=succinic acid; H2glu=glutaric acid) as the terminal ligands, which suggests a conceptual similarity to classical polyoxometalates. Even in the presence of competitive SO4(2-) in the assembly system, the CO3(2-) anion is still captured as a template to direct the formation of the Cu20 nanocluster, which indicates the stronger templation ability of CO3(2-) compared with SO4(2-). When other aliphatic dicarboxylates, such as glutaric acid, were used as ligands, the CO3(2-)-templated Cu20 nanocluster was maintained and acted as a cluster building unit (CBU) to be linked by two glutarate bridges to generate a distinct 1D metal-organic chain. This report presents not only a rare example of a huge anion-templated transition-metal cluster, but also its use as a robust CBU to construct novel coordination architectures. Variable-temperature magnetic susceptibility studies revealed that an antiferromagnetic interaction exists within the Cu20 nanocluster. The correlation between the coordination structure and the electron paramagnetic resonance spectra recorded of both powder and single-crystal samples are discussed in detail.
TL;DR: Subsequent application of the Mg3 Al-PW12 as catalyst in Knoevenagel condensation reactions of various aldehydes and ketones with Z-CH2 -Z' type substrates at 60 °C in mixed solvents demonstrated highly efficient catalytic activity.
Abstract: The family of polyoxometalate (POM) intercalated layered double hydroxide (LDH) composite materials has shown great promise for the design of functional materials with numerous applications. It is known that intercalation of the classical Keggin polyoxometalate (POM) of [PW12 O40 ](3-) (PW12 ) into layered double hydroxides (LDHs) is very unlikely to take place by conventional ion exchange methods due to spatial and geometrical restrictions. In this paper, such an intercalated compound of Mg0.73 Al0.22 (OH)2 [PW12 O40 ]0.04 ⋅0.98 H2 O (Mg3 Al-PW12 ) has been successfully obtained by applying a spontaneous flocculation method. The Mg3 Al-PW12 has been fully characterized by using a wide range of methods (XRD, SEM, TEM, XPS, EDX, XPS, FT-IR, NMR, BET). XRD patterns of Mg3 Al-PW12 exhibit no impurity phase usually observed next to the (003) diffraction peak. Subsequent application of the Mg3 Al-PW12 as catalyst in Knoevenagel condensation reactions of various aldehydes and ketones with Z-CH2 -Z' type substrates (ethyl cyanoacetate and malononitrile) at 60 °C in mixed solvents (V2-propanol :Vwater =2:1) demonstrated highly efficient catalytic activity. The synergistic effect between the acidic and basic sites of the Mg3 Al-PW12 composite proved to be crucial for the efficiency of the condensation reactions. Additionally, the Mg3 Al-PW12 -catalyzed Knoevenagel condensation of benzaldehyde with ethyl cyanoacetate demonstrated the highest turnover number (TON) of 47 980 reported so far for this reaction.
TL;DR: [Cu5(OH)4(H2O)2(A-α-SiW9O33)2](10-) (1) was tested as the first copper-containing polyoxometalate catalyst for O2 production via visible light-driven water oxidation.
TL;DR: A 2-fold interpenetrated porous POMOF is reported, which exhibits effective catalytic activity towards bromate reduction, using the methodology of extension for the reduced transition-metal-grafted ε-Keggin polyoxoanions with an expanded tripodal bridging ligand of H3BTB.
Abstract: Replacing the metal ions (or metal clusters) in routine MOFs with size-matched polyoxoanions to construct POM-based MOF materials (POMOF) combining well-defined crystalline structures, high surface area, regular and tunable cavities is the great challenge in the current POM chemistry area. In this work, we report a 2-fold interpenetrated porous POMOF, [TBA]6[H3PMo12O40]2[Zn8(BTB)2]·(∼35H2O), which exhibits effective catalytic activity towards bromate reduction, using the methodology of extension for the reduced transition-metal-grafted e-Keggin polyoxoanions with an expanded tripodal bridging ligand of H3BTB. The simultaneous TGA/DSC-MS technique was applied in this work to identify the evolved gases and was proved to be an effective method for analysing the decomposition process.