Polyoxometalate

About: Polyoxometalate is a research topic. Over the lifetime, 3493 publications have been published within this topic receiving 94123 citations. The topic is also known as: POM.

Ionothermal Synthesis of Five Keggin-Type Polyoxometalate-Based Metal-Organic Frameworks.

Abstract: Five unique Keggin-type polyoxometalate (POM)-based metal–organic frameworks (POMFs), namely [CH2L1]2[(CuL12)(PMoVI9MoV3O40)] (1), [Zn0.5(H2O)(L1)][Zn(L1)1.5Cl][H2L1]0.5[PMo12O40]·1.25H2O (2), (TBA)[Cu(H2O)2L12][PMo12O40] (3), [Cu2(H2O)2(L1)3][PMVI11MoVO40] (4), (H2L2)0.5[(CuIL2)2(PMo12O40)]·H2O (5), L1 = 4,4′-bis((1H-1,2,4-triazol-1-yl)methyl)-biphenyl, L2 = 1,4-bis((1H-1,2,4-triazol-1-yl)methyl)-benzene, have been synthesized under ionothermal conditions. According to single-crystal data, 1 exhibits a novel mechanically interlocked molecular architecture (MIMA) constructed by two-dimensional (2D) interpenetrating polyrotaxane layers with unique cyclophanes (tetra-cationic viologen macrocycle cyclobis(paraquat-p-phenylene) (CBPQT4+ system)), resulting in an H-bonded 3D supermolecule, and is the first synthesis of self-assembled cyclophane-PMOFs under ionothermal conditions. 2 shows a novel 2D three-fold interpenetrating polyrotaxane host and guest network. 1 and 2 are presented as the first MIMA polyrota...

New ionic crystals of oppositely charged cluster ions and their characterization.

Abstract: By reacting Keggin-type polyoxometalate cluster anions H2W12O406- (metatungstate) or CoIIW12O406- (tungstocobaltate) with the large aluminum cluster polycation [Al30O8(OH)56(H2O)26]18+, Keggin ion based molecular ionic compounds [δ-Al13O4(OH)24(H2O)12][XW12O40](OH)·nH2O (X = H2 (1) and Co (2); n ≅ 20) and [W2Al28O18(OH)48(H2O)24][H2W12O40]2·55H2O (3) were obtained. The polygon-shaped cluster ions are packed alternately through intercluster hydrogen bonds as well as electrostatic interactions, leaving large pores, which result from the packing of large clusters. The clusters are arranged in square pyramidal geometries, showing face-to-face interactions between them. The isolation of metastable [δ-Al13O4(OH)24(H2O)12]7+ and the formation of a new transition metal substituted aluminum heteropolycation [W2Al28O18(OH)48(H2O)24]12+ in 1−3 result from the slow fragmentation and recombination of Al30 in the presence of suitable counter cluster anions with similar shape and charge.

Controlled Interactions between Anhydrous Keggin-Type Heteropolyacids and Silica Support: Preparation and Characterization of Well-Defined Silica-Supported Polyoxometalate Species

Abstract: Anhydrous Keggin-type phosphorus heteropolyacids were deposited on partially dehydroxylated silica by using the surface organometallic chemistry (SOMC) strategy. The resulting solids were characterized by a combination of physicochemical methods including IR, Raman, 1D and 2D 1H, and 31P MAS NMR, electron microscopy experiments and density functional theory (DFT) calculations. It is shown that the main surface species is [≡Si(OH...H+)]2[H+]1[PM12O403−] where the polyoxometalate is linked to the support by proton interaction with two silanols. Two other minor species (10% each) are formed by coordination of the polyoxometalate to the surface via the interaction between all three protons with three silanol groups or via three covalent bonds formed by dehydroxylation of the above species. Comparison of the reactivity of these solids and of compounds prepared by a classical way shows that the samples prepared by the SOMC approach contain ca. 7 times more acid sites.

Inorganic–organic hybrid materials with different dimensions constructed from copper–fluconazole metal–organic units and Keggin polyanion clusters

Abstract: Inorganic–organic hybrid materials based on Keggin polyoxometalate building blocks combined with CuII/CuI and flexible fluconazole ligand [1-(2,4-difluorophenyl)-1,1-bis[(1H-1,2,4-triazol-1-yl)methyl]methanol] (Hfcz) have been obtained by hydrothermal methods, namely, [CuII2(Hfcz)4(SiW12O40)]·3H2O (1), [CuII4(fcz)4(H2O)4(SiMo12O40)]·6H2O (2), [CuII2(fcz)2][CuII4(fcz)4(SiW12O40)][CuII2(fcz)2(H2O)2(SiW12O40)]·6H2O (3), (Et3NH)2[CuI2(Hfcz)2(SiW12O40)]·2H2O (4), (Et3NH)2[CuI2(Hfcz)2(SiW12O40)]·H2O (5) and [CuI4(Hfcz)4(SiMo12O40)] (6). Their structures have been determined by single-crystal X-ray diffraction analyses, and the compounds are further characterized by elemental analyses, IR spectra and thermogravimetric (TG) analyses. In 1, Cu(II) cations are bridged by fluconazole ligands to form a 3D lvt coordination polymeric network, which is connected by (SiW12O40)4− anions to form a complicated 3D (4,6)-connected framework with the topology of (42·64)(46·67·82)2. In 2, two fcz− anions chelate two Cu2+ cations to form a [Cu(fcz)]22+ dimer, which is bridged by (SiW12O40)4−polyanions to generate a 2D (4,4) grid. Compound 3 is formed by three types of co-crystallizing subunits including a dimer [Cu(fcz)]22+, a dumbbell molecule [Cu4(fcz)4(SiW12O40)] and an infinite chain {[Cu2(fcz)2(H2O)2(SiW12O40)]2−}∞. In compounds 4 and 5, Hfcz ligands link Cu+ cations to generate 1D coordination polymeric units, and (SiW12O40)4−polyanions connect these metal–organic units to form two types of (63) sheets which are topological isomerism. In compound 6, (SiMo12O40)4−polyanions fixed in CuI–Hfcz square rings are further extended into a 2D sheet via linking CuI atoms of different rings. By carefully inspection of the structures of 1–6, it is believed that various transition-metal organic units and Keggin polyanions with different coordination modes are important for the formation of the different structures. In addition, electrochemical behaviors of compounds 1, 2, 5 and 6 have been investigated.

Catalytic oxidative desulphurization of gasoline using amphiphilic polyoxometalate@polymer nanocomposite as an efficient, reusable, and green organic–inorganic hybrid catalyst

Abstract: To preparation of ultra-clean gasoline fuel, a new amphiphilic nanocomposite (TBA-SiWMn@PVA) has been successfully synthesized by supporting sandwich-type silicotungstate polyoxometalate ((...