Synthesis and highly efficient photocatalysis applications of CdS QDs and Au NPs Co-modified KTaO3 perovskite cubes.

Perovskite structure has attracted interest for the past few years due to its prospects in photocatalysis. The exploration of efficient perovskite photocatalysts still receives much attention in the field of chemistry and materials science. Herein, KTaO3 cubes are first prepared by hydrothermal synthesis, then Au nanoparticles (NPs) are loaded on the cubes by photodeposition, and finally, CdS quantum dots (QDs) are modified on Au/KTaO3 cubes using an in situ growth method, and eventually tantalum-based photocatalysts in a ternary system are successfully prepared. The fabricated CdS/Au/KTaO3 reveals photocatalytic properties in hydrogen evolution and degradation of dyes. In particular, under the same conditions, the photocatalytic hydrogen evolution rate of the optimized 13%CdS/1.3%Au/KTaO3 (13% and 1.3% are the contents of CdS and Au in the composite photocatalyst, respectively) is 2.892 mmol g-1 h-1. Compared to those of bare KTaO3 and CdS, it is approximately 107-fold and 8.5-fold enhanced, respectively. And the sizes of CdS and Au in the photocatalyst are 4.21 and 15.07 nm. The increased photoactivity of the composite can be ascribed to the synergistic effect of several factors, such as: the Au NPs' surface plasma resonance (SPR) impact improves the production of hot electrons and the ability of KTaO3 to capture light; effective integration between CdS QDs and KTaO3 cubes forms a heterojunction and expands the absorption range of KTaO3 in the visible light spectrum, improving the utilization rate of visible light effectively. Hence, a co-modification strategy has been proposed for endowing KTaO3 perovskites with new structures and different functions, and it is expected to become a general strategy to find an illuminating strategy for achieving improvements and enhancements in the photocatalytic field.

Ultrathin Niobate Nanosheet Assembly with Au NPs and CdS QDs as a Highly Efficient Photocatalyst.

Niobate nanosheets have aroused widespread interest in recent years for their prospects in catalysis. The exploration of 2D niobate catalysis with stable and efficient properties is still the focus in chemistry and materials science. Herein, the successful fabrication of 2D CdS/Au/HNb3 O8 catalyst is demonstrated which revealed efficient photocatalytic properties in H2 evolution, oxidative self-coupling of amines to imines, and degradation of dyes. Especially the assembled architecture can give a rate of 5.85 mmol ⋅ g-1 ⋅ h-1 of photocatalytic H2 evolution, an ∼254-fold enhancement, compared with bare HNb3 O8 nanosheets under identical conditions. In accordance with density functional theory (DFT) and X-ray adsorption fine structure (XAFS) analyses, the vast improvements are benefited from efficient migration and separation of charge carriers. Besides, the surface plasma resonance (SPR) effect of Au NPs enhances the light harvesting capacity and boosts the generation of hot electrons, efficiently improving the visible-light absorption.

Three rare-earth incorporating 6-peroxotantalo-4-selenates and catalytic activities for imidation reaction.

Functionalization with belt lanthanide groups allows for the crystallization and structural characterization of homometallic selenotantalates, CsK[Ln(H2O)6Se4(TaO2)6(OH)3O18]·nH2O (Ln = Eu/Gd, n = 14 (STD-Eu, STD-Gd) and Ln = Lu, n = 12 (STD-Lu)). The basket-shaped {Se4(TaO2)6} archetype is assembled in a simple one-pot reaction of Na2SeO3 and K8[Ta6O19]·17H2O in acidic aqueous medium (pH 2) and in the presence of hydrogen peroxide. This unit has been proven to be an effective precursor for the preparation of a range of new POMs containing the {Se4(TaO2)6} unit. The lanthanide derivatives STD-Eu, STD-Gd and STD-Lu have been fully characterized with single-crystal X-ray diffraction, IR spectroscopy, TG analysis and PXRD in the solid state. The photoluminescence and lifetime decay behaviours of STD-Eu have been studied at room temperature, and the photoluminescence spectrum displays the characteristic emission of the Eu3+ cation. In addition, the catalytic activities of STD-Eu, STD-Gd and STD-Lu on the reaction of phthalic anhydride with phenylamines have been investigated. STD-Eu shows good catalytic activities for imidation reactions.

Two novel telluroniobates with efficient catalytic activity for the imidation/amidation reaction.

We present the synthesis and catalytic properties of two novel telluroniobates {Te15Nb21} and {Te10Nb14}. {Te15Nb21} is the first trimeric telluroniobate with the largest number of tellurium atoms in the Te-Nb system. Besides, both clusters exhibit excellent catalytic activity in the amidation reactions of anhydrides and amines, and cyclic imides and bi-amides can be controllably synthesized, which represents a breakthrough in the catalysis of polyoxoniobates.

A large molecular cluster with high proton release capacity.

We present a single molecular polyoxometalate cluster (K41[(P2W12Nb6O62)6{Mn3(OH)3(H2O)6}4{Mn3Na(H2O)16}]·26H2O) with controllable release of a large number of protons (∼40 per molecule) in its aqueous solution upon addition of a base. The deprotonation/protonation process is reversible with the clusters remaining intact. This molecule can also absorb up to 11 protons per cluster when an acid, HCl, was added to its original aqueous solution. To the best of our knowledge, such large proton absorption/release capacity along with excellent stability is unprecedented.

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.

Discovery of the selenotantalate building block and its lanthanide derivatives: design, synthesis, and RhB decolorization properties.

Recently, we demonstrated that the in situ formation of a building block is an attractive synthesis strategy for creating novel clusters with controllable structures. Herein, we present the design and synthesis of the first tantaloselenite polyoxoanion [Se4(TaO2)6(OH)4O17]4- (1) and a series of lanthanide derivatives (RE3+ = Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Yb3+). In total, we report seven clusters that vary in both composition and structure but which share the same {Se4(TaO2)6} building block. The compounds are fully characterized by single-crystal X-ray diffraction, IR spectra, TG, and PXRD and their decolorization properties for RhB have also been investigated. Compound 1 exhibits good photocatalytic activity for the decolorization of RhB while the introduction of lanthanide into the framework can also maintain this activity.

Shape-control of CeF3 nanocrystals by doping polyoxometalates: syntheses, characterization and tunable photoluminescence.

A series of CeF3 nanocrystals with uniform morphologies have been synthesized by introducing various polyoxometalates as dopants and shape modifiers. The results indicate that the shape and photoluminescence of the CeF3 nanocrystals could be finely tuned by changing the component and amount of the polyoxometalates.

Organometallic functionalized non-classical polyoxometalates: synthesis, characterization and electrochemical properties.

Two monomeric non-classical tellurium-containing heteropolymolybdate-supported metal carbonyl derivatives (NH4)5H3{[Te2Mo12(OH)O44][Mn(CO)3]}·18H2O (1) and (NH4)8{[Te2Mo12(OH)O44][Re(CO)3]}·13H2O (2) have been successfully isolated in good yields. Compounds 1 and 2 are the first two examples of metal carbonyl derivatives of heteromolybdate with tellurium as the central atom. These two compounds have been thoroughly characterized by single-crystal X-ray diffraction, elemental analyses, X-ray powder diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and UV-Vis spectroscopy. The electrochemical catalytic activities of 1 and 2 including cyclic voltammetry and catalytic oxidation of nitrite have also been investigated.

A high-nuclearity isopolyoxotungstate based manganese cluster: one-pot synthesis and step-by-step assembly.

A manganese(iii,iv)-tungsten(vi) supercluster based on 72 manganese ions (48 MnIV and 24 MnIII) and 48 tungsten(vi) centers [{MnIV24MnIII12O28(H2O)23}2(W24O120)2]40- has been prepared from the carboxylic Mn12 cluster. Its structure comprises two unprecedented cage-like Mn36W24 cores linked via two Mn-O-W bonds, leading to a Mn72W48 assembly. The inorganic synthetic mechanism was investigated through different synthesis methods and comprehensive ESI-MS tests.

Immobilization of carbonyl rhenium tripods on the surface of a trinickel-substituted Dawson-type polyoxotungstate.

A monomeric trinickel(ii)-substituted phosphotungstate [H9P2W15O62Ni3]9- ion is stabilized by grafting three {Re(CO)3} organometallic groups on the surface for the first time. Magnetic measurements manifest that the resulting complex, Na(NH4)5[P2W15O56Ni3(H2O)3(µ3-OH)3(Re(CO)3)3]·18H2O (1), displays overall ferromagnetic interactions with the presence of ZFS for Ni2+ at low temperature.

The Polyoxovanadate-Based Carboxylate Derivative K6H[VV17VIV12(OH)4O60(OOC(CH2)4COO)8]·nH2O: Synthesis, Crystal Structure, and Catalysis for Oxidation of Sulfides.

The high-nuclearity polyoxovanadate-based carboxylate derivative K6H[VV17VIV12(OH)4O60(OOC(CH2)4COO)8]·nH2O (1) has been successfully synthesized by conventional aqueous methods and structurally characterized. The [VV17VIV12(OH)4O60(OOC(CH2)4COO)8]7- polyanion is built up from three cages: one {VV17(OH)4O44} cage and two identical [(VIV3O6)2(OOC(CH2)4COO)4]8- cages. Of the three cages, the {VV17(OH)4O44} is a purely inorganic polyoxovanadate cluster, whereas each of the [(VIV3O6)2(OOC(CH2)4COO)4]8- cages is a vanadium-based organic-inorganic hybrid cluster framed via four adipate ligands linking simultaneously to two triangular {V3} units. The two [(VIV3O6)2(OOC(CH2)4COO)4]8- cages are covalently attached to the central {VV17(OH)4O44} cage via V-O-V bonds in a linear arrangement, resulting in a {V29}-based hybrid cluster skeleton. The catalytic properties of compound 1 for the oxidation of sulfides by tert-butyl hydroperoxide were investigated, and the result indicates that 1 exhibits excellent catalytic activity for the oxidation of sulfides under mild conditions.

Synthesis, characterization and catalytic epoxidation properties of lanthanide-stabilized peroxoisopolytungstates.

A series of new lanthanide-containing peroxoisopolyoxotungstates, K6Na4[H32{Ln4(WO4)(H2O)16[W7O22(O2)2]4}3]·105H2O [Ln = CeIII (1), NdIII (2), SmIII (3), TbIII (4), ErIII (5)], have been successfully synthesized and structurally characterized. All polyanions [Ln(WO4)(H2O)16{W7O22(O2)2}4]14- are isostructural and consist of a central [Ln(WO4)(H2O)16]10+ cluster surrounded by four peripheral [W7O22(O2)2]6- units. They could act as efficient recyclable catalysts for the epoxidation of various alkenes including different cycloalkenes, styrene derivatives, internal and long-chain alkenes. Under optimal conditions, catalyst 2 displays the best catalytic activity for the oxidation of cyclooctene with high cyclooctene conversion (98.3%) and excellent selectivity (up to 99%) and could be reused for three cycles with a negligible decrease in reactivity.

Synthesis, structure, and luminescent properties of a family of lanthanide-functionalized peroxoniobiophosphates.

Eight new lanthanide derivatives containing 6-peroxoniobio-4-phosphate building block, [LnIII(H2O)6]2[H4(NbO2)6P4O24]·nH2O [Ln = Eu (1), Gd (2), Tb (3), Dy (4), Ho (5), Er (6), Tm (7), Yb (8), 1-5, 7, 8 n = 12; 6 n = 9], have been successfully obtained using an in-situ strategy and fully characterized in the solid state by single-crystal X-ray diffraction, IR spectra, TG-MS, PXRD. Structural analyses indicate that these isostructural polyanions 1-8 consist of one [P4(NbO2)6O24]10- (P 4 (NbO 2 ) 6 ) clusters and two pendant Ln3+ cations. In these compounds, P 4 (NbO 2 ) 6 clusters are connected by lanthanide cations to form extended two-dimensional architectures. The approach takes advantage of the ability of in-situ formed P 4 (NbO 2 ) 6 cluster to build frameworks by using it as ligands to lanthanide ions. The photoluminescence (PL) and lifetime decay behaviors of 1, 3 and 4 in solid state have been performed at room temperature. The PL emission of 1, 3 and 4 is mainly derived from the characteristic 5D0→7FJ (J = 1, 2, 3, 4), 5D4→7FJ (J = 6, 5, 4, 3) and 4F9/2→6H J (J = 15/2, 13/2, 11/2) transitions of the EuIII, TbIII and DyIII cations, respectively.

Assembly of TeO32- Ions Embedded in an Nb/O Cage with Selective Decolorization of Organic Dye.

A novel 24-niobic-2-tellurite, [H2Te2Nb24O72]14-, was isolated by incorporating tellurite anions into a polyoxoniobate cage. The synthesized cluster represents the first example of a sandwich-type polyoxoniobate with the largest telluroniobate aggregate. Furthermore, the hybrid material acts as an efficient catalyst for the decolorization of basic fuchsin.

A Monomeric Tricobalt(II)-Substituted Dawson-Type Polyoxometalate Decorated by a Metal Carbonyl Group: [P2W15O56Co3(H2O)3(OH)3Mn(CO)3]8.

A monomeric tricobalt(II)-substituted phosphotungstate polyanion, [H9P2W15O62Co3]9-, is stabilized by the attachement of an organometallic group, {Mn(CO)3}, for the first time. The resulting polyoxometalate-supported [Mn(CO)3]+ complex (1) can be used as an efficient catalyst in the cycloaddition of CO2 with epoxides under mild reaction conditions with pyrrolidinium bromide as a cocatalyst. Besides, magnetic measurements show that the compound exhibits weaker ferromagnetic interactions at low temperature.

Two New Tetravacant Organometallic Keggin-Type Heteropolyoxomolybdates-Supported Manganese Carbonyl Derivatives.

Two novel heteropolyoxomolybdate [XMo8O31]n- (X = Ge(1) or P(2)) manganese carbonyl derivatives [(CH3)4N]6H6{MnII(GeMo8O31)[MnI(CO)3]2}2·12H2O (1) and [(CH3)4N]4H6{MnII(PMo8O31)[MnI(CO)3]2}2·14H2O (2), have been successfully synthesized and characterized in the solid state by single crystal X-ray diffraction, IR and thermogravimetric analysis, and in solution by UV-Vis spectroscopy and electrochemistry. The two polyoxomolybdate-based organometallic compounds 1 and 2 represent rare examples of transition metal sandwich-based polyoxometalate metal carbonyl derivatives (PMCDs), in which the organic-inorganic hybrids are composed of four Mn(CO)3⁺ groups symmetrically occupied the tetravacant sites of dimeric heteropolyoxomolybdate {Mn2(XMo8O31)2}n- through MnI-O-Mo bonds. The carbonyl functionalized Mn atoms are octahedrally coordinated via three µ2-oxygens of the [XMo8O31]n- unit and three carbonyl carbon atoms. Interestingly, 1 and 2 form a psedocuboidal ring Mn(CO)3Mo3O12 with {Mn(CO)3}⁺ occupying the three fold axis of the Mo3O12 octahedral triad. Beside this, the two centrally placed adjacent MnII atoms show intramolecular Mn∙∙∙Mn interactions of 3.11 and 3.16 Å in 1 and 2, respectively. Significant n→π* and O···O intermolecular interactions between the orthogonally aligned adjacent carbonyl groups through the overlap of lone-pair electrons on oxygen atoms with the antibonding orbital (π*) of the adjacent carbony carbon atom of the subsequent units in 1 and 2 were observed. The electrochemical properties of the two compounds were also been investigated.

Discovery of Heteropolytantalate: Synthesis and Structure of Two 6-Peroxotantalo-4-phosphate Clusters.

Polyoxometalates (POMs) of Nb and Ta are greatly different from those of Mo, W, and V that have been studied extensively and developed well. The latter can be formed simply by acidification of their aqueous monomeric oxoanions and has found application areas from catalysis to magnetism, materials science, medicine, and nanotechnology. Even now the polyoxoniobate (PONb) chemistry has accelerated dramatically over the last 15 years, and a vast expansion of available PONbs has been reported. However, after nearly 200 years of POM research, Ta-based POM chemistry is still at its infant stage and only dominated by the isopolyoxotantalate ions (Ta6 and Ta10) and transition-metal-capped Ta6 species, along with two Ti-substituted polyoxotantalates [Ti2Ta8O28]8- and [Ti12Ta6O44]10- reported very recently. In this study, we discover two novel peroxotantalophosphate clusters [P4(TaO2)6O25]12- (1) and [P4(TaO2)6O24]10- (2) by incorporating phosphorus heteroatom into Ta-oxo framework, which represent the first two examples of heteropolytantalate. Interestingly, two P2Ta3 half-units are cis- and trans-condensed in 1 and 2, leading to "open" and "closed" configurations, respectively. These two chemically and structurally related clusters can be isolated in a controlled manner, and the yields are relatively high. Both compounds were characterized in the solid state by single-crystal X-ray diffraction, 31P MAS NMR, FT-IR, TGA, and elemental analysis as well as by 31P NMR in solution. The results presented here provide a strategy to be applicable to other heteroatom-incorporated polyoxotantalates and further expand the phase space for polyoxotantalate chemistry.

Discovery and isolation of the trans-isomers of two 1 : 2-type lanthanide-containing monolacunary Dawson-type tungstophosphates: [LnIII(α2-P2W17O61)2]17- (Ln = La, Ce).

Two novel trans-isomers of 1 : 2-type lanthanide-containing monolacunary Dawson-type tungstophosphates [Ln(α2-P2W17O61)2]17- (Ln = LaIII (1), CeIII (2)) were successfully isolated and characterized by elemental analysis, IR, TG, and 31P NMR studies. Both polyanions 1 and 2 consist of one Ln3+ ion sanwiched between two monolacunary Dawson-type tungstophosphates fragments [α2-P2W17O61]10- oriented at 180° with respect to each other. The solid-state and solution 31P NMR spectroscopy revealed that the trans-[Ce(α2-P2W17O61)2]17- species probably quickly isomerizes to the cis-isomer species in solution.

{Fe3Nb25} cluster based on an Fe-centred Keggin unit.

A new heteropolyniobate, [Fe3Nb25O76]18-, persists in aqueous solution by means of electrospray ionization mass spectrometry. It has been synthesized and characterized by IR, TGA, EDX-SEM, magnetic and single-crystal X-ray diffraction, and it features an Fe-centred Nb-Keggin unit {Fe3Nb10}.