Deoxygenation of Polynuclear Metal-Oxo Anions: Synthesis, Structure, and Reactivity of the Condensed Polyoxoanion [(C(4)H(9))(4)N](4)(NbW(5)O(18))(2)O

2D-2D lattice engineering route for intimately coupled nanohybrids of layered double hydroxide and potassium hexaniobate: Chemiresistive SO2 sensor

2D-2D lattice engineering route is used to synthesize intimately coupled nanohybrids of layered double hydroxide (LDH) and potassium hexaniobate. The 2D-2D lattice engineering route is based on the electrostatically derived self-assembly of delaminated zinc-chromium-layered double hydroxide (ZC-LDH) nanosheets and potassium hexaniobate (HNb) nanosheets (ZCNb nanohybrids). The 2D-2D lattice-engineered ZCNb nanohybrids display expanded surface area, mesoporous anchored nanosheets network morphology, and intimate coupling between nanosheets. The 2D-2D lattice engineered ZCNb nanohybrids are used for the low temperature operated gas sensor. The ZCNb nanohybrids display outstanding selectivity for the SO₂, with the high response of 61.5% compared to pristine ZC-LDH (28.08%) and potassium niobate (8%) at 150 °C. Moreover, ZCNb sensors demonstrate superior response and recovery periods of 6 and 167 s at 150 °C, respectively. This result underscores the exceptional functionality of the ZCNb nanohybrids as efficient SO₂ sensors. Moreover, these findings vividly demonstrate that the 2D-2D lattice-engineered ZCNb nanohybrids are quite effective not only in improving the gas sensor activity but also in developing of new type of intimately coupled mesoporous LDH-metal-oxide based hybrid materials.

Unraveling the Effects of Cobalt on Crystal Growth and Solution Behavior of Nb6P2W12-based Dimeric Clusters

We report the synthesis, characterization, and solution self-assembly of plenary Nb₆P₂W₁₂-based transition-metal substituted polyoxometalate, which is obtained by simply adding transition metals (Co²⁺) into aqueous solution containing cluster [(NbO₂)₆P₂W₁₂O₅₆]^12-, which is obtained by an in situ synthetic method. The incorporation of Co²⁺ ions significantly affects the crystal structure, resulting in the formation of a 1D chain-like crystal and the first example of a niobotungstate-based cobalt derivative cluster. The behavior and stability of this cluster in solution are confirmed by time-resolved static light scattering, dynamic light scattering, small-angle X-ray scattering, and electrospray mass spectrometry studies.

Insight into the reactivity of in situ formed {(NbO2)3SiW9}: synthesis, structure, and solution properties of a trimeric polytungstosilicate trapping a {MnNb9} core

The first example of the trimeric polyoxometalate cluster, Cs₁₀Na₃[(SiW₉Nb₃O₃₈)₃MnO₃(H₂O)₃]·18H₂O (1a), has been synthesized using an in situ synthetic strategy and thoroughly characterized.

Two new members of the niobium-substituted polytungstophosphate family based on hexalacunary [H2P2W12O48]12− building blocks

Herein we present two structurally novel nanoscale clusters [{Nb₆(O₂)₄P₂W₁₂O₅₇}₂]²⁰⁻ (1) and [{P₂W₁₂Nb₇O₆₃(H₂O)₂}₄{Nb₄O₄(OH)₆}]³⁰⁻ (2) formed by controlling the reaction parameters.

Bridging the opposite chemistries of tantalum and tungsten polyoxometalates

Reaction of Ta peroxometalate and tungstate affords the first systematic series of Ta/W isopolyoxometalates. An analogous reaction system yields a Nb/W cluster. The electronic structure and stability of these clusters varies as a function of the group V metal content, as inferred from spectroscopic, electrochemical and mass-spectrometry analysis and confirmed by DFT calculations.

Structural evolution in polyoxometalates: a DFT study of dimerization processes in Lindqvist and Keggin cluster anions

Density functional theory (DFT) calculations are used to investigate dimerization, by acid condensation, between Lindvist and Keggin cluster anions. When specific addendum atoms are present (notably, Ti, V, Nb, and Cr), these clusters dimerize in the presence of acid via the formation of mu-O linkages. These processes may be viewed as molecular models for the formation of metal-oxygen bonds in the active sites of metalloenzymes, or in materials chemistry, and we here provide detailed information concerning these reactions. For this, DFT calculations are used to provide insight into the mechanism(s) associated with dimerization of Lindqvist clusters, W5MO19(n-) (M = W, Mo, V, Nb, and Ti) in acidic media. In full accord with experimental data, our calculations show that dimerization of Nb and Ti derivatives is thermodynamically favored and that this is not the case for dimerization between Mo, V, and W addendum atoms. In addition, dimerization of PW11TiO40(5-) and SiW11NbO40(5-) to give the corresponding dimers was also calculated to be exothermic. Two possible mechanisms, involved in two competing pathways, are evaluated and discussed. Conclusions are presented concerning the role played by the nature of the metal atoms taking part in M-mu-O-M bond formation. A correlation is established between the relative strengths of specific terminal M=O bonds in monomeric precursors and the tendency of these to form M-mu-O-M bonds.