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The non-classical KP6Mo18O73heteropolyanion has been studied by the density functional theory (DFT) method, and the calculated geometry compares well with the experimental one. In fully oxidized [KP6Mo18O73]7−state, the dxy-orbitals centered at eight “belt” Mo sites in the lower part of the “basket” are the major contributors to the LUMO and LUMO+1, while the LUMO+2 orbital is mostly focused on the two polar parts. In contrast, the HOMOs indicates that the coordination of the KP6Mo18heteropolyanion to metal ions favorably occurs at the oxygen atoms from four external phosphates and two molybdates of the handle of the “basket”. Compared with Wells–Dawson [P2Mo18O62]6−, the HOMO–LUMO gap in fully oxidized [KP6Mo18O73]7−is much smaller, indicating much easier reduction that is consistent with the cyclic voltammogram. Both frontier orbitals and Mulliken analysis indicate that two of three blue electrons in [KP6Mo18O73]10−(KP6Mo18-3e) have spin alpha while third blue electron has spin beta, in agreement with magnetic data. The four-copper complex of the non-classical KP6Mo18-3e heteropolyanion has been synthesized and structurally characterized; its structure supports the theoretical results such as reactivity and basicity of external oxygen sites. [ABSTRACT FROM AUTHOR]

The non-classical KP6Mo18O73heteropolyanion has been studied by the density functional theory (DFT) method, and the calculated geometry compares well with the experimental one. In fully oxidized [KP6Mo18O73]7−state, the dxy-orbitals centered at eight “belt” Mo sites in the lower part of the “basket” are the major contributors to the LUMO and LUMO+1, while the LUMO+2 orbital is mostly focused on the two polar parts. In contrast, the HOMOs indicates that the coordination of the KP6Mo18heteropolyanion to metal ions favorably occurs at the oxygen atoms from four external phosphates and two molybdates of the handle of the “basket”. Compared with Wells–Dawson [P2Mo18O62]6−, the HOMO–LUMO gap in fully oxidized [KP6Mo18O73]7−is much smaller, indicating much easier reduction that is consistent with the cyclic voltammogram. Both frontier orbitals and Mulliken analysis indicate that two of three blue electrons in [KP6Mo18O73]10−(KP6Mo18-3e) have spin alpha while third blue electron has spin beta, in agreement with magnetic data. The four-copper complex of the non-classical KP6Mo18-3e heteropolyanion has been synthesized and structurally characterized; its structure supports the theoretical results such as reactivity and basicity of external oxygen sites. [ABSTRACT FROM AUTHOR]

An ionothermal reaction has generated a cobalt hydroxyacetate magnet that contains a three-dimensional Co–O–Co framework consisting of vertex-sharing octahedral chains bridged by another octahedra viaedge-sharing and shows spin glass behavior. [ABSTRACT FROM AUTHOR]

The electrocatalytic splitting of water to produce hydrogen is regarded as an efficient and promising strategy but is limited by its large overpotential; thus, a highly efficient electrocatalyst is urgently needed. Mixed metal doping is an important strategy in defect engineering because the heteroatoms can change the intrinsic structure to form defects by affecting the atomic coordination mode and adjusting the electronic structure, which is often accompanied by morphological changes. Herein, two-dimensional layered bimetallic Co–pydc containing axially coordinated water molecules was selected by producing surface defects through Fe doping in Co centers as bifunctional electrocatalysts for OER and HER. The optimized Co0.59Fe0.41–pydc possesses outstanding OER performance with the lowest overpotential of 262 mV to reach j = 10 mA cm−2, and Co0.75Fe0.25–pydc possesses superior HER performance with the lowest overpotential of 96 mV at j = 10 mA cm−2. Furthermore, the overall water splitting device assembled with Co0.59Fe0.41–pydc@NF//Co0.59Fe0.41–pydc@NF affords a current density of 10 mA cm−2 at only 1.687 V. This work emphasizes the surface defects formed by tuning the electronic structure of metal centres accompanied with morphological changes of bimetallic dopants for efficient overall water splitting. [ABSTRACT FROM AUTHOR]

Purple of Cassius is a pigment based on a gold colloid that has been known for hundreds of years. It has had a profound influence on modern nanoscience. But the origin of the small size of the Au nanoparticles (NPs) and their superior stability remains ambiguous. The experiments and characterization studies discussed here confirmed that SnCl2 functioned not only as a reducing agent but also as an effective surface capping agent through bimetallic Au–Sn bonding. This finding expands the types of Au NP stabilizer from traditional organic examples (e.g., thiolate or phosphine) to metallic examples. The formation of a Au–Sn interface also endows Au NPs with excellent activity and separability for the hydration of alkynes to ketones. [ABSTRACT FROM AUTHOR]

The design and utilization of dual sites for synergistic catalysts has been recognised as an efficient method towards high-efficiency catalysis in the cyanosilylation of aldehydes, which gives key intermediates for the synthesis of a number of valuable natural and pharmaceutical compounds. However, most of the reported dual-site catalysts for this reaction were homogeneous, accompanied by potential deactivation through internal complexation of the dual sites. Herein, by the rational selection of an uncoordinated tertiary nitrogen based tricarboxylic ligand (tris[(4-carboxyl)-phenylduryl]amine, H3TCBPA), a new three-dimensional calcium-based metal–organic framework (MOF), Ca3(TCBPA)2(DMA)2(H2O)2 (1, where TCBPA = ionized tris[(4-carboxyl)-phenylduryl]amine and DMA = N,N-dimethylacetamide), possessing accessible dual catalytic sites, Lewis-basic N and Lewis-acidic Ca, has been designed and constructed by a one-pot solvothermal reaction. As expected, 1 is capable of dually and heterogeneously catalysing the cyanosilylation of aldehydes at room temperature, and can be reused for at least 6 runs with a maximum turnover number (TON) of 1301, which is superior to most reported cases. Additionally, 1 shows CO2 adsorption ability and conversion with epoxides, which is beneficial for the establishment of a sustainable society. [ABSTRACT FROM AUTHOR]

Lanthanide metal–organic frameworks (Ln-MOFs) have demonstrated great potential in luminescence sensing and optical anti-counterfeiting. High-security anti-counterfeiting technology is of great importance and requires the development of universal luminescent materials with multiple modes of emission and adjustable photoluminescence. Herein, a 3D red light emission microporous europium(III) metal–organic framework [Eu3(OH)(1,3-db)2(H2O)4]·3H2O (1) (1,3-db = 1,3-di(3′,5′-dicarboxylpheny) benzene) was constructed from a zigzag [Eu3(COO)8] chain and π-electron-rich terphenyl-tetracarboxylate. Notably, the quenched fluorescence of 1 under hydrogen chloride vapor could be recovered upon fuming by a vapor of Et3N. Most strikingly, the strong blue light emission by nitrogen and sulfur co-doped carbon dots (N,S-CDs) could be encapsulated in 1 to generate a dual-emission composite, namely, N,S-CDs@Eu-MOF, which shows solvent-dependent photoluminescence: N,S-CD-related blue luminescence in water and Eu-MOF-related red emission in organic solvents. Taking advantage of the above unique reversible fluorescent behavior, Eu-MOF and N,S-CDs@Eu-MOF are prepared as fluorescent high-security inks to achieve data encryption and decryption on specific flower patterns. [ABSTRACT FROM AUTHOR]

Discrete supertetrahedral clusters of metal chalcogenides are rare because of the difficulty involved in meeting global charge matching between the negative charge of the skeleton and counterion. We present herein the third type of a discrete chalcogenide cluster with a double T3 structure in the compound (HDBN)6[In20S33(DBN)6] (DBN = 1,5-diazabicyclo [4.3.0]-5-nonene), the anion of which features quasi-D3 symmetrical double-T3 In20S33 supertetrahedra with six cornered indium atoms coordinated by DBN molecules. DFT theory calculations of the interaction between host and guest show that this compound may have high kinetic stability and low photoelectric reactivity. [ABSTRACT FROM AUTHOR]

Isostructural mixed alkali/alkaline-earth metal tellurite halides BaLiTe2O5X (X = Cl, Br) have been successfully synthesized by a mild hydrothermal method, which possess the [Te2O5]∞ chains formed by the corner-sharing connections of the TeO3 and TeO4 polyhedra. The [Te2O5]∞ chains are bridged via the LiO3 polyhedra to form the [LiTe2O5]∞ layers with 4- and 6-membered rings. The adjacent [LiTe2O5]∞ layers are linked via the BaO9 polyhedra to form the [BaLiTe2O5]∞ double layers, which are further connected via weak Ba–X–Li interactions to generate a 3D framework. Analysis of different lithium tellurites shows that the different arrangements of the Te–O and Li–O units in the lithium tellurites can be attributed to the cation–cation repulsion and lone-pair effect. Both compounds display good thermal stability, wide optical bandgaps (4.25 and 4.13 eV), and large birefringence. First-principles calculations indicate that the TeOn groups and X− determine the optical properties of BaLiTe2O5X (X = Cl, Br). [ABSTRACT FROM AUTHOR]

Strategies for developing efficient energy conversion and storage devices that have been optimized by designing electrode materials is a critical challenge for researchers. Herein, we report the design and synthesis of a series of Co@NC trifunctional electrocatalysts derived from rationally designed cobalt-added anion MOF precursors and preliminarily reveal the relationship between the precursor and corresponding efficient electrocatalysts. Benefiting from the special composition of Co2+-doped anion MOFs involving Co2+ chelates as the Co2+ sources, the resulting CoT@NC electrocatalyst possesses abundant Co/Co–Nx/Co–Ox and multiple active nitrogen sites that are evenly distributed. As expected, the rich variety of active species and hierarchical pore structures endow CoT@NC with excellent performances toward ORR, HER, and OER, including a high half-wave potential value of 0.86 V for ORR and low overpotential values for OER (350 mV) and HER (209 mV) at 10 mA cm−2 in an alkaline solution. Moreover, we assembled a conventional Zn–air battery with CoT@NC as the air-cathode catalyst, which exhibited excellent rechargeable performance and ultrahigh durability. Moreover, CoT@NC coated on Ni foam was used as both anode and cathode for the overall water-splitting process, which needed a bias voltage of 1.70 V to achieve a current density of 10 mA cm−2. This study sheds light on the design, fabrication, and regulation of highly active cobalt-based electrocatalysts with abundant active sites and tunable pore structures for electrocatalysis and other applications. [ABSTRACT FROM AUTHOR]

Exploring efficient and stable oxygen evolution reaction (OER) catalysts with earth-abundant elements has been an urgent task in water splitting. Metal–organic frameworks (MOFs), possessing abundant active metal sites and tunable porous crystalline structures, are promising as OER catalysts. In this paper, a MOF based on benzotriazole-5-carboxylate (Co3-btca) that contains unsaturated coordinated metal centers and a 1D channel was selected to act as an OER catalyst. To optimize the OER performance, isostructural bimetallic and trimetallic frameworks were obtained by doping with Fe and/or Ni ions. The optimized Co2.36Fe0.19Ni0.45-btca possesses the lowest overpotential of 292 mV at 10 mA cm−2 and a small Tafel slope of 72.6 mV dec−1. The enhanced catalytic performance could be attributed to the synergistic effect between the unsaturated coordinated Co, Fe and Ni sites, which are beneficial for the nucleophilic attack of OH− forming adsorption intermediates. [ABSTRACT FROM AUTHOR]

Silver doped TiO2 (Ag–TiO2) materials show high activity and good stability in photocatalysis, but the mechanism could not be illustrated clearly due to their imprecise and inhomogeneous characteristics. Ag-doped titanium-oxo clusters (Ag-TOCs) with an exact crystal structure, which are rarely reported, are beneficial for further understanding structure–property relationships. Herein, six new Ag-TOCs with a butterfly-like Ti8Ag2 core have been synthesized through facile solvothermal reactions, in which two Ag ions are successfully linked to the surface of the Ti8 core. Of interest, the Ti6 unit of the Ti8Ag2 core is similar to that found in the anatase structure and may be a promising model for Ag–TiO2 materials. The band gaps of these Ag-TOCs show different values mainly affected by different ligands. DFT calculations revealed that the lowest energy bands of Ag-TOCs are attributed to the Ag-to-TiO core charge transfer bands. Additionally, all Ag-TOCs exhibit good photoelectric response and high photodegradation activity towards organic dyes. [ABSTRACT FROM AUTHOR]

Two new alkali–metal bismuth iodates KBi(IO3)3(OH) (1) and NaBi(IO3)4 (2) have been synthesized by a hydrothermal method via tuning of alkali–metal ions. Compound 1 crystallizes in the space group P1̅ and features a [Bi(IO3)3(OH)]n chain with eight-membered Bi–O–I–O–Bi–O–I–O rings. The [Bi(IO3)3(OH)]n chain consists of paddlewheel-like dimeric Bi2(OH)2(IO3)4 units linked by IO3 pairs. Compound 2 in the polar space group Cc features a [Bi(IO3)4]− double layer with Bi4I4 eight-membered rings (8-MRs). NaBi(IO3)4 exhibits a strong second harmonic generation (SHG) response of ∼5.0 × KDP (KH2PO4) and a wide transmittance window (0.4–12 μm), and structure analyses and theoretical calculations reveal that polarization results mainly from the proper alignment of the IO3 groups. The calculated electronic structure based on the DFT method indicates that the BiOn and IO3 groups dominate their optical properties. [ABSTRACT FROM AUTHOR]

A novel and thermally stable aluminum phosphate Li6Na3Sr14Al11P22O90 (1) has been achieved by using a solid-state molten method, which contains an oxo-centered trinuclear cluster and an anti-Lowenstein's rule Al–O–Al linkage and is constructed from two types of (3,6)-connected kgd layers [Al(Al3O)(PO4)7]25− and [Al(PO4)2]3−. The good optical transparency in the whole UV range and excellent thermal stability make the title compound a potential optical window material. [ABSTRACT FROM AUTHOR]

Density functional theory calculations combined with the energy and building-block decomposition analyses have been carried out to investigate the structures, stability orders, redox potentials and proton binding of the six Baker–Figgis isomers (α, β, γ, α*, β* and γ*) of [(SbO6)W18O54(OH)2]9− {H2SbW18} and [(NaF6)W18O54(OH)2]7− {H2NaW18} anions at the level of PBEsol-D3/TZP. Both bonding energy and Gibbs free energy analyses exhibit that the two non-classical Wells–Dawson (WD) species behave quite differently from each other. The pyroanimonate {H2SbW18}, with a stability order of γ* ＞ β* ＞ α ＞ α* ＞ β ＞ γ, is a non-classical WD species, while the hexafluoride {H2NaW18} (α ＞ β ＞ γ ＞ γ* ＞ β* ＞ α*) is a transition intermediate between classical and non-classical WD types, possessing both non-classical ([XW18O60(OH)2]n−, X = I, Te and W) and classical [Si2W18O62]8− properties. Energy decomposition analyses (EDA) reveal that spatial arrangement (Ehost), host–guest fragment interaction energy (FIE), and structural distortion energy (DE) are three key factors governing the relative stability of isomers; among these, DE is always dominant, while FIE and Ehost are subordinated but are still important. Building-block decomposition analyses (BDA) disclose that the octahedral {MO6} units of the equatorial belt, particularly the staggered belt, are always more distorted than those of the two polar caps inside each structure. The theoretical redox potentials demonstrate that the oxidizing power increases with a trend of α ＜ β ＜ γ and α* ＜ β* ＜ γ* for both species, and the first redox potential is closely related to the energy level of the LUMO of each anion. Evaluation of the proton inclusion energies suggests that {H2NaW18} can only embed two protons, while {H2SbW18} may encapsulate four; the number of embedded protons is controlled by both the charge of the heteroatom X and the volume of the tetrahedral {O4}/{OF3} cavity. [ABSTRACT FROM AUTHOR]

The reversible crystal transformation between the mononuclear complex [Cu(tzbc)2(H2O)4] (1) and the 4-fold interpenetrated diamondoid MOF [Cu(tzbc)2] (2) was chemically implemented and structurally interpreted. Interestingly, despite 4-fold interpenetration, desolvated 2 with 1D channels and rich N-groups shows exclusive CO2 adsorption of up to 12.5 wt% at room temperature and low pressure, indicating potential application in the separation of industrial and automobile exhaust. [ABSTRACT FROM AUTHOR]

An expanded pyridyl-decorated MOF-505 analogue[Cu2(L)(H2O)2]·Gx (H4L = 5,5′-(pyridine-2,5-diyl)diisophthalic acid, G = solvent molecule) has been solvothermally synthesized and reported. It exhibited rare hierarchical meso- and microporosity. With exposed unsaturated CuII sites and Lewis basic pyridyl sites, the material shows both large CO2-uptake capacity (123.4 cm3 g−1 at 273 K, 1 bar) and high selectivity for CO2 over N2 (55.7) at 273 K. Furthermore, for the first time the compound has been exploited for its heterogeneous catalytic performance toward the cyanosilylation reaction under solvent-free conditions. The compound can be recycled up to five times with only a minor loss of activity. [ABSTRACT FROM AUTHOR]

The butterfly-like tetranuclear cobalt cluster based 3D MOF [Me2NH2][Co2(bptc)(μ3-OH)(H2O)2] (1) underwent a reversible thermally triggered single-crystal-to-single-crystal transformation via Co–Owater weakened intermediate 1a to produce a partly dehydrated phase [Me2NH2][Co2(bptc)(μ3-OH)(H2O)] (2), which was confirmed by single-crystal X-ray diffraction, powder X-ray diffraction, thermogravimetric analysis, and IR spectroscopy. During the dehydration course, the local coordination environment of one Co2+ ion was changed from the saturated octahedron to a coordinately unsaturated square-pyramid, accompanied by a crystal color change from red to purple. Compared with pristine hydrated 1, dehydrated 2 exhibits highly efficient and recyclable catalytic activity for cyanosilylation of carbonyl compounds with a low catalyst loading of 0.1 mol% Co at room temperature under solvent-free conditions, which due to the open Co2+ sites as catalytically activated sites played a significant role in the heterogeneous catalytic process. [ABSTRACT FROM AUTHOR]

A perfectly aligned 63 helical tubular cuprous bromide single crystal has been synthesized and characterized, which can selectively decompose negatively charged dyes of Methyl Orange (MO) and Kermes Red (KR), and the photocatalytic efficiency is higher than that of nanosized (∼25 nm) TiO2 and ZnO. The direction and magnitude of the dipole moments as well as the band structure were calculated to reveal high photocatalytic efficiency. Moreover, luminescence studies indicate that the CuBr tube materials show very strong yellowish green emissions in the solid state and emulsion even at room temperature, and exhibit extremely high detection sensitivity towards nitro-explosives via fluorescence quenching. Detectable luminescence responses were observed at a very low concentration of 20 ppm with a high quenching efficiency of 94.90%. The results suggest that they may be promising multifunctional materials for photo-catalysis, luminescence and sensing of nitro-explosives. [ABSTRACT FROM AUTHOR]

A new interpenetrated bioactive nonlinear optical metal–organic framework [Zn2(ppa)2(1,3-bdc)(H2O)] has been designed and synthesized, which shows both a high drug content of 63.9% and a good slow release effect in simulated physical conditions compared to other non-interpenetrated bioactive MOFs. It also shows a large powder second-harmonic generation (SHG) efficiency of 5.6 times that of KH2PO4 (particle size: 150–200 μm). [ABSTRACT FROM AUTHOR]

A novel two-dimensional (2D) azido-based CuII network, [Cu11(pic)6(N3)16] (1), was prepared using picolinic acid (Hpic) as coligand. Interestingly, 1 is composed of symmetric double azido EO-bridged [Cu(N3)2]n chains linked by [Cu(pic)2] units making a regular ladder with a missing rung. These rung-defected ladders are assembled in a layered structure by long azido-CuII contacts between neighboring [Cu(N3)2]n chains. The magnetic properties of 1 are dominated by significantly strong antiferromagnetic coupling (J/kB = −15.4(2) K) between CuII spins through the double EO azido-bridges along the [Cu(N3)2]n chains. [ABSTRACT FROM AUTHOR]