Construction of a unique 2-D layered vanadoborate with water-assisted proton conductivity

In the present work, a new two-dimensional layered vanadoborate Na4[V12B18O54(OH)6(H2O)]•(H2en)4•2(OH)•3H2O (1, en = ethylenediamine), based on a [V12B18O54(OH)6(H2O)]10- cluster unit, was hydrothermally obtained and characterized. In the structure, the clusters...

Water assisted high proton conductance in a pure-inorganic framework vanadoborate

A pure-inorganic framework vanadoborate is successfully synthesized under hydrothermal conditions and exhibits good proton conductivity.

Transition-Metal-Modified Vanadoborate Clusters as Stable and Efficient Photocatalysts for CO2 Reduction

Photocatalytic carbon dioxide reduction (CO₂RR) is considered to be a promising sustainable and clean approach to solve environmental issues. Polyoxometalates (POMs), with advantages in fast, reversible, and stepwise multiple-electron transfer without changing their structures, have been promising catalysts in various redox reactions. However, their performance is often restricted by poor thermal or chemical stability. In this work, two transition-metal-modified vanadoborate clusters, [Co(en)₂]₆[V₁₂B₁₈O₅₄(OH)₆]·17H₂O (V₁₂B₁₈-Co) and [Ni(en)₂]₆[V₁₂B₁₈O₅₄(OH)₆]·17H₂O (V₁₂B₁₈-Ni), are reported for photocatalytic CO₂ reduction. V₁₂B₁₈-Co and V₁₂B₁₈-Ni can preserve their structures to 200 and 250 °C, respectively, and remain stable in polar organic solvents and a wide range of pH solutions. Under visible-light irradiation, CO₂ can be converted into syngas and HCOO^- with V₁₂B₁₈-Co or V₁₂B₁₈-Ni as catalysts. The total amount of gaseous products and liquid products for V₁₂B₁₈-Co is up to 9.5 and 0.168 mmol g^-1 h^-1. Comparing with V₁₂B₁₈-Co, the yield of CO for V₁₂B₁₈-Ni declines by 1.8-fold, while that of HCOO^- increases by 35%. The AQY of V₁₂B₁₈-Co and V₁₂B₁₈-Ni is 1.1% and 0.93%, respectively. These values are higher than most of the reported POM materials under similar conditions. The density functional theory (DFT) calculations illuminate the active site of CO₂RR and the reduction mechanism. This work provides new insights into the design of stable, high-performance, and low-cost photocatalysts for CO₂ reduction.

Efficient proton conductivity of a novel 3D open-framework vanadoborate with [V6B20] architectures

A new three-dimensional (3-D) inorganic metal-oxygen network vanadoborate Na3H10[Ni(H2O)2(VO)6(B10O22)2]·NH4·19H2O (1) constructed from lantern-type {(VO)6(B10O22)2} clusters, NaO6 polyhedra and NiO6 octahedra, was successfully synthesized by a hydrothermal method. In the structure, the {V6B20} clusters are linked together through NiO6 octahedral bridges, resulting in 1-D chains along the c-axis. The 1-D chains are further connected by NaO6 polyhedra to give rise to a 3-D open-framework structure. Furthermore, lots of NH4+ and H2O molecules are accommodated in the void of the structure, and may interact with the [V6B20] system via N-HO, O-HO hydrogen bonds, constructing a complex hydrogen-bonding network system. Strikingly, compound 1 exhibited a high proton conductivity of 3.22 × 10-3 S cm-1 at 50 °C under 100% RH with an activation energy of 1.66 eV.

Vanadoborates: cluster-based architectures, preparation and properties

The different connections of [VO_x] (x = 4, 5, 6) and [AO_x] (A = B, x = 3, 4; A = P, x = 4) polyhedral units ultimately result in a fascinating variety of vanadoborate anionic clusters.

Study on the source of magnetic properties of three novel boratopolyoxovanadates via two-dimensional infrared correlation spectroscopy

Three novel polyoxovanadoborates namely [V₁₂B₁₈O₄₆(OH)₁₄(H₂O)_0.75]·20.5H₂O 1, Na₂[V₁₂B₁₈O₄₈(OH)₁₂(H₂O)_0.5]·26.5H₂O 2 and Cd_0.5{[Na(H₂O)₂]2[Na(H₂O)]₂[Na(H₂O)₃]2V₁₂B₁₈O₅₃(OH)₇(H₂O)_0.5}·11H₂O 3 have been hydrothermally synthesized and structurally characterized. The boratopolyoxovanadate cage [V₁₂B₁₈O₆₀] backbones in 1-3 are constructed by the combination of two hexameric oxovanadate units [V₆O₉] and one puckered [B₁₈O₄₂] ring via sharing O atoms. All three compounds were obtained under alkaline conditions, and the cluster anions were all [V₁₂B₁₈O₆₀]. But the cations were different, it is inferred that the protonation of the three compound cluster ions is different, respectively [V₁₂B₁₈O₄₆(OH)₁₄(H₂O)_0.75] in 1, [V₁₂B₁₈O₄₈(OH)₁₂(H₂O)_0.5]^2- in 2 and [V₁₂B₁₈O₅₃(OH)₇(H₂O)_0.5]^7- in 3. The V oxidation states ratio of V^IV to V^V were 2:1 confirmed by valence bond calculation and XPS. We studied the magnetic properties of three compounds by two methods: The variable temperature magnetic susceptibility and the 2D IR COS under magnetic perturbation. From the 2D IR COS under magnetic perturbation map, it is showed that all three: (1) the presence of V^IV. (2) Certain quasi-aromaticity from B₃O₃ six-membered ring. (3) The difference of protonation and the charge of the cluster anions. This work enriches the theory of two-dimensional correlation spectroscopy and also provides a new approach to the study of magnetic materials.

A CsCl-type inorganic cluster-based high-symmetry crystal built from {Mo4.55V7.45PO40}10.45- with a high ratio of vanadium to molybdenum and {(H2O)0.3@K6(H2O)12}6+ clusters exhibiting proton conduction below the freezing point of water

As a class of anionic oxoclusters of early transition metals in their highest oxidation states, polyoxometalates (POMs) show considerable structural versatility and unique chemical and physical properties, making them promising multifunctional materials. In this study, a Keggin-type POM has been achieved, with a formula of [(H2O)0.3@K6(H2O)12]H4.45[PV7.45Mo4.55O40]·11H2O (1), and its microcrystals and nanocrystals have been obtained, respectively. This POM was characterized by elemental analysis for C, H and N, ICP-MS, TG, PXRD, SEM, X-band EPR and XPS techniques. Single crystal X-ray diffraction analysis demonstrated that 1 shows a rare extended structure with a high-connected three-dimensional (3D) all inorganic network of a Keggin-type POM, built from {Mo4.55V7.45PO40}10.45- polyoxoanions and {(H2O)0.3@K6(H2O)12}6+ clusters with CsCl-type crystal structure. In addition, to the best of our knowledge, 1 shows the highest ratio of vanadium to molybdenum among Keggin-type POMs reported thus far. Most interestingly, 1 exhibits intrinsic proton conduction below the freezing point of water, with a proton conductivity of 6.90 × 10-7 S cm-1 at 249 K and further reaching 3.36 × 10-6 S cm-1 at 272 K and Ea = 0.44 eV at 249-272 K.

A New 3-D Open-Framework Zinc Borovanadate with Catalytic Potentials in α-Phenethyl Alcohol Oxidation

A novel 3-D open-framework zinc borovanadate [Zn₆(en)₃][(VIVO)₆(VVO)₆O₆(B18O36(OH)₆)·(H₂O)]₂·14H₂O (1, en = ethylenediamine) was hydrothermally obtained and structurally characterized. The framework was built from [V12B18O54(OH)₆(H₂O)]10- polyanion clusters bridged by Zn(en) complex fragments. The compound not only possessed a three-dimensional open-framework structure with unique plane-shaped channels, but also exhibited excellent catalytic activities for the oxidation of α-phenethyl alcohol.

All-Inorganic Ionic Porous Material Based on Giant Spherical Polyoxometalates Containing Core-Shell K6 @K36 -Water Cage

This work demonstrates that the use of high-negative and high-symmetry lacunary polyoxometalates (POMs) for the clustering of alkali metal ions is a feasible strategy not only for the formation of rare high-nuclearity alkali-metal clusters but also for the construction of new-type all-inorganic ionic porous materials. By the strategy, an unprecedented high-nuclearity K-H₂ O cluster {K₄₂ (H₂ O)₆₀ } with core-shell K₆ @K₃₆ configuration is stabilized by 8 C_3v -symmetry trivacant POMs [GeW₉ O₃₄ ]^10- , forming a novel giant ionic alkali-metal-POM composite cluster {K₄₂ Ge₈ W₇₂ O₂₇₂ (H₂ O)₆₀ } with more than 100 metal centers. The incorporated 42-nuclearity K-H₂ O cluster {K₄₂ (H₂ O)₆₀ } exhibits the highest-nuclearity alkali-metal-water cluster known to date in POM chemistry. Further, the giant {K₄₂ Ge₈ W₇₂ O₂₇₂ (H₂ O)₆₀ } clusters can be linked by another kind of alkali metal ions Na⁺ to generate a fascinating three-dimensional all-inorganic ionic porous framework with high chemical stability, proton conductivity, and water vapor adsorption.

Proton conduction in a new 3-D open-framework vanadoborate with an abundant hydrogen bond system

A 3-D hydrogen bond-enriched vanadoborate was successfully synthesized under hydrothermal conditions and it exhibited good proton conductivity.

A new 3-D open-framework Li-rich vanadoborate and its high ionic conductivity after transforming into glasses

A Li-rich vanadoborate was transformed into its glassy phase at 220 °C, which then exhibits high ionic conductivity.