Xiya Yang

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.

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.

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.

Keggin Arsenomolybdate Based Hybrid Compound with Complementary Inorganic Double Helical Chains

A new Keggin arsenomolybdate based inorganic–organic hybrid compound containing complementary inorganic double helical chains, [Ag2(pyttz)3(H2O)][HAsMo12O40]·H2O (1), was successfully synthesized and characterized. Single crystal X-ray analysis reveals that compound 1 exhibits 3D supramolecular framework with (43)(44·62)(47·610·84) topology, in which the complementary double helical chains constructed by the left- and right-handed helical chains are found. In the crystal engineering point of view, the rich coordination atoms and conjugated heterocyclic rigid plane of pyttz organic ligand and the multiple twisted V-shaped coordination modes of Keggin POMs facilitate the formation of the inorganic helical structure. In addition, the title compound exhibits good photocatalytic degradation of methylene blue dye, and is very stable and easily separated from the catalytic system for reuse as well.

Two new silver triazole frameworks with polyoxometalate templates

Two new polyoxometalate-templated organic–inorganic hybrid compounds with different metal–organic frameworks, [Ag5(trz)6][H4PMo12O40] (1) and [Ag10(trz)8][HPMo12O40] (2) (trz = 1,2,4-triazole), have been prepared based on the same organic ligands under different pH values. Compound 1 exhibits a honeycomb 2D [Ag5(trz)6] network and 3D graphite-like hybrid framework, and compound 2 exhibits a 3D {Ag3[Ag6(trz)6][Ag(trz)2]} framework with 2D channels, in which [PMo12O40]3− polyanions locate in the center of channels. To the best of our knowledge, [PMo12O40]3− polyanions represent the highest coordination number in 1 and terminal oxygen coordination number in 2 of Keggin POMs up to date. A comparison of two compounds demonstrates that the coordination mode of 1,2,4-triazole ligands and Keggin POMs templates have important influences on the assembly of different frameworks. In addition, compounds 1 and 2 exhibit good photocatalytic degradation of Rhodamine-B, and are very stable and easily recyclable as well.