Jing-Quan Sha

The factors affecting on the assembly of Ag–H2biim system: size, charge or shape of polyanions?

By introducing different polyoxotungstates into the Ag–H2biim system, four new compounds with distinct architectures, Ag2(H2biim)4(W6O19)·2H2O (1), Ag6(H2biim)6(SiW12O40)(OH)2·2H2O (2), Ag6(H2biim)6(PW12O40)(OH)3·H2O (3) and Ag6(H2biim)6(P2W18O62)·12H2O (4) (H2biim = 2,2′-biimidazole), have been hydrothermally synthesized, and characterized by routine physical methods and single crystal X-ray diffraction. In compound 1, the Lindqvist type polyoxotungstate {W6} combines with the chelate Ag–H2biim complex forming a discrete “dumbbell-like” motif. Isostructural compounds 2 and 3 are obtained by introducing Keggin polyoxotungstates ({SiW12} and {PW12}, respectively), which show a 2D layer structure. The 2D layers parallel each other to form a 3D supramolecular framework. The larger Wells–Dawson polyoxotungstate {P2W18} directs the formation of compound 4, in which one 2D layer is the inversion of the neighboring ones. Furthermore, there exist infinite Ag chains in compounds 2–4, which are quite unusual in POM-based compounds. The distinction among the final four architectures is ascribed to the structure-directing effect of different polyanions. The electrochemical properties of compounds 1–4 are studied. In addition, the antibacterial properties of the four compounds against negative Escherichia coli (E. coli) and positive Staphylococcus aureus are investigated.

Polyoxometalate-Incorporated Metallapillararene/Metallacalixarene Metal-Organic Frameworks as Anode Materials for Lithium Ion Batteries

A series of remarkable crystalline compounds containing metallapillararene/metallacalixarene metal-organic frameworks (MOFs), [Ag5(pyttz)3·Cl·(H2O)][H3SiMo12O40]·3H2O (1), [Ag5(trz)6][H5SiMo12O40] (2), [Ag5(trz)6][H5GeMo12O40] (3), and [Ag5(trz)6][H4PW12O40] (4) (pyttz = 3-(pyrid-4-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl, trz = 1,2,4-triazole), have been obtained by using a simple one-step hydrothermal reaction of silver nitrate, pyttz for 1 and trz for 2-4, and Keggin type polyoxometalates (POMs). Crystal analysis reveals that Keggin POMs have been successfully incorporated in the windows of the metallapillararene/metallacalixarene MOFs in compounds 1-4. In addition, the Keggin silicomolybdenate-based hybrid compounds 1 and 2 were used as anode materials in lithium ion batteries (LIBs), which exhibited promising electrochemical performance with the first discharge capacities of 1344 mAh g-1 for 1 and 1452 mAh g-1 for 2, and this stabilized at 520 mAh g-1 for 1 and 570 mAh g-1 for 2 after 100 cycles at a current density of 100 mA g-1. The performances are better than that of (NBu4)4[SiMo12O40] matrix and commercial graphite anodes.

A rigid organic ligand-induced POMCP with a helical self-penetrating structure as a redox and acid catalyst

By the utilization of rigid organic ligands, a new POMCP with inorganic helical configuration features was isolated and structurally characterized, in which inorganic double chains are constructed from POMs and single Ag ions, and the contribution of the rigid ligand to the helical structure of POMCPs is firstly reported and discussed. In particular, the new POMCP displays good acid-catalytic activity toward the synthesis of aspirin and photocatalytic selectivity for the degradation of organic dyes, as well as excellent photocatalytic activity toward the degradation of MB. Finally, the catalytic reaction kinetics are also discussed.

Construction and catalytic activities of polyoxometalate-based compound containing helical chains

Abstract A polyoxometalate-based, inorganic–organic hybrid compound containing a helical structure along the a axis, [Ag(pyttz)2][H2PW12O40]·2H2O (p-pyttz = 3-(pyrid-4-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl), has been isolated and structurally characterized. Single-crystal X-ray diffraction analysis reveals that the new compound possesses two helical channels constructed by the left- and right-handed helical chains, respectively, which are fused together through sharing POMs dimer fabricating a 3-D framework with {44·53·63} {44·53·63} topolopy. The new compound displays good acid-catalytic activity toward the synthesis of Aspirin and good oxidation-catalytic activity to the decomposition of Rhodamine B dye; the catalytic reaction kinetics are discussed.

Hydrothermal Synthesis, Characterization and Electrocatalytic/Photocatalytic Activities of New Polyoxometalate Based Hybrid Compound

In this paper, we report the hydrothermal synthesis and physicochemical characterization of a complicated high-dimensional and high-connected POM-based hybrid compound, namely, [Ag3(pytz)2(H2O)]2.[HAgGeMo12O40]·H2O, which has been synthesized by reactions of pyridyltetrazoles and Keggin POMs. X-ray diffraction and crystallographic analyses reveals that the new compound exhibits POMs chains pillaring transition-metal complexes, which represents the highest coordination number of Keggin POMs up to date. Moreover, the new compound bulk-modified carbon-paste electrode (1-CPE) displays good electrocatalytic activity toward the reduction of nitrite, and the result of the photocatalytic activities indicates that the new compound presents better degradation activity and may be a potential photocatalyst to oxidative decomposition of rhodamine B dye in the presence of crystals [Ag3(pytz)2(H2O)]2·[HAgGeMo12O40]·H2O catalyst under ultraviolet-light irradiation.

Polyoxometalates Templated Metal Ag–Carbene Frameworks Anodic Material for Lithium-Ion Batteries

A POMs templated 3D Ag-carbene framework with lvt-a topology was hydrothermally synthesized. The POMs templated MCF combining the advantages of POMs, MOFs, and carbene not only shows excellent thermal and chemical stabilities but also possesses a good discharge capacity of 481 mAh·g-1 after 100 cycles applied as anode material in LIBs.

Construction, PPy loading and photocatalytic performance of a polyoxometalate-templated metallacycle compound

Abstract A polyoxometalate-templated metallacycle compound, [Ag6trz6][H3PMo12O40]2·6H2O (trz = 1,2,3-triazole), has been isolated and structurally characterized. The compound represents the first example of a trigonal antiprism based metal-organic framework (MOFs) with complicated Zr6Br12 type topology, in which the trigonal antiprisms as building blocks are constructed by the Ag6trz6 space polygons and the bifunctional POMs (both as template and building block). In addition, to improve the photocatalytic activity of polyoxometalate-templated metallacycle compound, polypyrrole was loaded on its surface through a chemical oxidation polymerization process in situ. Finally, the photocatalytic activity of [Ag6trz6][H3PMo12O40]2 and PPy@[Ag6trz6][H3PMo12O40]2 under visible light was explored, and the results demonstrate that the PPy loading on the surface of POMs-based hybrid compound is feasible to improve their photocatalytic performance.

Synthesis and polypyrrole-loading study of antifungal medicine fluconazole functionalized Keggin polyoxotungstates

Abstract To rich the coordination polymer and polyoxometalate (POM) chemistry, two new hybrid compounds based on Keggin POMs with antifungal medicine fluconazole (Hfkz = [1-(2,4-difluorophenyl)-1,1-bis [(1H-1,2,4-triazol-1-yl)-methyl]methanol]), [Ag4(Hfkz)2][PW12O40] (AgFkzPW12) and [Ag4(Hfkz)2][SiW12O40] (AgFkzSiW12), have been successfully synthesized and structurally characterized. Moreover, to improve the photogenerated electron-hole pair separation properties, the surface of hybrid compounds was loaded by polypyrrole (PPy) through a chemical oxidation polymerization process in situ fabricating hybrid nanocomposites AgFkzPW12@PPy and AgFkzSiW12@PPy. As a result, the Hfkz molecules were successfully grafted onto the surface of the Keggin polyoxoanions, and their nanocomposites exhibit better photocatalytic activity than the respective matrix compounds under the irradiation of visible light.

Assembly of Multifold Helical Polyoxometalate-Based Metal–Organic Frameworks as Anode Materials in Lithium-Ion Batteries

For exploring the multifold helical fabrication of polyoxometalate (POM)-based hybrid compounds, four POM-based crystalline compounds with different meso-helices, H3[Ag27(trz)16(H2O)6][SiW12O40]2·5H2O (1), H[Ag27(trz)16(H2O)4][PW12O40]2·2H2O (2), [Ag23(trz)14(H2O)2][HSiW12O40] (3), and [Ag23(trz)14(H2O)2][PW12O40] (4), were successfully isolated by using the delicate 1,2,3-triazole ligand and silver ions in this work. Crystal analysis reveals that compounds 1 and 2 and compounds 3 and 4 are isomorphous and display 2-/4-fold mixed meso-helices and simple 2-fold meso-helices, respectively. In addition, due to the reversible multielectron redox behavior and electron storage functions of POMs, compounds 1 and 3 were studied as anode materials in lithium-ion batteries (LIBs). Compounds 1 and 3 show very high lithiation capacities (1356 and 1140 mAh g-1, respectively) in the initial cycle, which are much higher than those of (NBu4)4[SiW12O40] and commercial graphite at the current density of 100 mA g-1. More importantly, both compounds also show good stable performance after 100 cycles.

Influence of ammonium polyphosphate on flame-retardant behavior and smoke suppression property of EVA/magnesium hydroxide composites

ABSTRACT To overcome the flammability and smoke generation of EVA, samples with different mass fraction of magnesium hydroxide (MH) and ammonium polyphosphate (APP), have been prepared by internal mixer and cured by compression molded. The fire characteristics including smoke and heat production of EVA composites were studied by cone calorimeter test (CCT), limiting oxygen index test, UL-94 test, scanning electron microscopy, and thermogravimetric (TG) analysis, respectively. For the sample EVA5 loading 10.0 mass% APP and 40.0 mass% MH, the LOI value can be increased to the value of 31.1 and reach V-0 level. The CCT test showed that APP and MH could significantly improve the fire safety of EVA. Remarkably, the peak of heat release rate, the peak of smoke production rate, and total smoke release for EVA5 were decreased by 75.4%, 88.1% and 70.8% compared with pure EVA, respectively. TG test showed that APP promoted the char formation in the degradation process of EVA; as a result, the residual carbon was increased. The results indicated that APP combined with MH could facilitate the formation of the rigid intumescent char and obviously enhance the flame retardancy, smoke suppression and thermal stability of the EVA matrix.