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The development of a sensitive and efficient detection technology for trace toxic hexavalent chromium (Cr(VI)) in water is a pressing concern. In this study, an hourglass-type phosphomolybdate-based metal–organic network with the formula [Na0.5Cu5.5(H2O)2(btmbp)4][Mn(H2O)3]2{Mn[H6P4Mo6O31]2}·10H2O (1, btmbp = 4,4'-bis((1H-1,2,4-triazol-1-yl)methyl)biphenyl) was hydrothermally synthesized. The crystal network consists of a ladder-like two-dimensional layered structure constructed by vertical connections of one-dimensional (1D) [Na0.5Cu5.5(H2O)2(btmbp)4]6+ metal–organic chains and 1D inorganic polyanionic chains. Compound 1 exhibits excellent electrochemical property and a wide light absorption range including visible light to accelerate the electron transfer in redox processes. When serving as a photoassisted electrochemical (PAEC) sensor for trace Cr(VI) detection, compound 1 exhibits a high sensitivity of 330.5 μA·μM−1 and a low detection limit of 0.95 nM (98.79 ppt) along with high anti-interference ability and excellent PAEC detection stability, outperforming most reported polyoxometalate-based sensors and equaling noble-metal sensors, far satisfying World Health Organization standards for Cr(VI) concentration in drinking water. This work provides a new photoelectrochemical sensor material for monitoring environmental pollutants.

The exploration of high-efficiency photocatalysts to drive the conversion of highly toxic heavy metal hexavalent chromium (Cr(VI)) in wastewater to low-toxic trivalent chromium (Cr(III)) is of great significance for purifying water that contains emerging contaminants. Herein, four hourglass-type phosphomolybdate-based hybrid networks—(H2bpe)2[M(H2O)3]2{M[P4Mo6O31H7]2}·8H2O (M = Mn for 1, Co for 2) and (Hbpe)(H2bpe)Na[M(H2O)3]2{M[P4Mo6O31H7]2}·9H2O (M = Mn for 3, Co for 4; {M[P4Mo6O31H7]2}8− (abbr. M{P4Mo6}2); bpe = 1,2-di(4-pyridyl)ethylene)—were hydrothermally synthesized as heterogeneous photocatalysts for Cr(VI) reduction. A structural analysis showed that the four hybrids 1–4 exhibited two-dimensional inorganic sheet-like structures with a 3,6-connected kgd topology built of hourglass phosphomolybdate clusters having different central metal ions, which further interacted with organic bpe cations via abundant hydrogen-bonding interactions to extend the structure to a three-dimensional (3D) supramolecular network. The four hybrids displayed excellent redox properties and wide visible-light absorption. When used as heterogeneous photocatalysts, hybrids 1–4 exhibited excellent photocatalytic activity for Cr(VI) reduction under 10 W white light irradiation, with reduction rates of 91% for 1, 74% for 2, 90% for 3, and 71% for 4, respectively, within 80 min. The Cr(VI) reduction reaction over hybrids 1–4 followed the pseudo first-order kinetics model with reaction rate constants k of 0.0237 min−1 for 1, 0.0143 min−1 for 2, 0.0221 min−1 for 3 and 0.0134 min−1 for 4, respectively. The Mn{P4Mo6}2-based hybrids 1 and 3 showed better photocatalytic performance than the Co{P4Mo6}2-based hybrids 2 and 4, along with excellent recycle stability. This mechanism study shows that the different central metals M in the M{P4Mo6}2 cluster have a considerable impact on photocatalytic performance due to their regulation effect on the electronic structure. This work provides evidence for the important role of the central metal in hourglass-type phosphomolybdate in the regulation of photocatalytic performance, and it brings inspiration for the design of highly efficient photocatalysts based on polyoxometalates.

The various researches on different sub-areas of artificial intelligence (AI) in China are discussed. These sub-areas include mathematics mechanization, automated reasoning, temporal and spatial knowledge, natural language processing, and intelligent diagnosis. The application of the insights gained from this research and the future direction AI research in China is also discussed.

The flexible organic ligands 1,3-bis(1,2,4-triazol-1-yl)propane (btp), 1,4-bis(1,2,4-triazol-1yl)butane (btb) and 1,6-bis(1,2,4-triazol-1-yl)hexane (btx) are introduced into the Wells-Dawson polyoxometalates (POM) system, which has aimed at obtaining novel architectures of POM coordination polymers with a combination of flexibility and robustness. The structural analyses has shown that the length of flexible bis(triazole) ligands and metal ion coordination geometries have a synergic influence on the structures of this series.

Reactions of the fulvenes CHC( R R) [( R = CHCH, R = CH ( 1); R = R = CH ( 2); R, R = (CH) ( 3), R, R = (CH) ( 4)] with Mo(CO) in refluxing xylene gave the corresponding cyclopentadienyl dimolybdenum carbonyl complexes [(η-CHCR′R′Mo(CO)] [( R′ = CHCH, R′ = CH ( 5); R′ = R′ = CH ( 6); R′, R′ = CH(CH) ( 7); R′, R′ = CH(CH) ( 8)], which were characterized by elemental analysis, IR and H NMR spectra. The molecular structures were determined by single-crystal X-ray diffraction. The results indicated the exocyclic double bond of the ligands 1 and 2 changed into a single bond and the exocyclic double bond of the ligands 3 and 4 underwent a double-bond isomerization process. [ABSTRACT FROM AUTHOR]

Three diruthenium carbonyl complexes, namely ( η: η-CHC(CH))Ru(CO) ( 1), ( η: η-CHC(CHCH)(CH))Ru(CO) ( 2), and ( η: η-CHCH)Ru(CO) ( 3), were obtained from the reactions of CHC(Me), CHC(Et), and CHC(CH), respectively, with Ru(CO) in refluxing xylene. The complexes were characterized by elemental analysis, IR and H NMR spectra. Single-crystal X-ray diffraction analysis for complexes 1 and 2 revealed that the fulvene ligands bridge two ruthenium atoms in η: η fashion. [ABSTRACT FROM AUTHOR]

Two one-dimensional transition-metal-centered polyoxotungstates, that is, [Cu(en)][Cu(en)(HO)][Cu(en)(phen)][CuWO]·3HO ( 1) (en = ethylenediamine, phen = phenanthroline) and [Cu(en)][Cu(en)(HO)][VWO(VO)]·3HO ( 2) have been synthesized hydrothermally and structurally characterized by elemental analyses, IR spectroscopy, electrochemical analysis, thermogravimetric analysis and X-ray single crystal diffraction. Single-crystal structural analysis reveals that both of them represent one-dimensional structures constructed from transition-metal-centered Keggin-type polyanions bridged by secondary metal coordination groups of Cu-ligand. Noticeably, compound 1 exhibits a helical chain-liked structure, and the anion is coordinated by three Cu-ligand units, representing a copper-centered and tri-supported Keggin structure. In compound 2, the polyoxoanion [VWO(VO)] represents a V-centered tetra-capped pseudo-Keggin structure, and is coordinated by four Cu-ligand units. The three-dimensional supramolecular structures of compounds 1 and 2 are constructed through intermolecular hydrogen bonding interactions. The electrochemical and thermalstable properties of 1 and 2 are also studied. The results show the redox properties of polyoxotungstates are retained in title polymers. [ABSTRACT FROM AUTHOR]

A rare [W6O22]8−fragment has been first captured in aqueous solution of [W6O19]2−by using a transition-metal complex and isolated as a new compound [Cu4(W6O22)(L1)2(H2O)2]·2H2O (1; L1 = 2-amino-4,6-bis(2-pyridyl)pyrimidine), indicating that [W6O19]2−could also transform to [W6O22]8−in aqueous solution besides the earlier proven ψ-metatungstates, [W10O32]4−, β-[(H2)W12O40]6−and [W7O24]6−. [ABSTRACT FROM AUTHOR]

A series of seven mixed-ligand coordination polymers, namely {[Cd4(H2L1)4(suc)4]·3H2O}n(1), {[Cd4(H2L1)3(suc)4]·5H2O}n(2), {[Cd2(HL1)2(suc)]·8H2O}n(3), {[Cd(H2L2)(suc)]·3H2O}n(4), {[Cd(H2L3)(suc)]·3H2O}n(5), {[Co(H2L1)(chdc)(H2O)]·H2O}n(6), {[Co(H2L2)(chdc)(H2O)]}n(7) have been produced by the reaction of three 2-amino-4,6-dipyridylpyrimidine isomers (H2L1, H2L2, H2L3) and secondary ligand 1,4-succinic acid (H2suc) or 1,4-cyclohexanedicarboxylic acid (H2chdc) with Cd(II) and Co(II) salts under hydrothermal conditions. All these compounds have been structurally determined by elemental analysis, IR and single-crystal X-ray diffraction. The three isomers are introduced in a mixed-ligand system for the first time. For the H2L1–H2suc–Cd(II) system, it is found that the structures of compounds 1–3exhibiting a 1-D double-chain, a rare 1-D quadruple nano-chain and a 2-D network with (6,3) topology, respectively, are influenced by the ratio of metal-to-ligand. When H2L2 and H2L3 were used instead of H2L1, two 1-D chains (compounds 4and 5) were obtained. Although they have the same molecular formula and structure motif, their supramolecular networks constructed by hydrogen-bondings and π–π stacking interactions are different. When H2L1 and H2L2 were introduced into the Co(NO3)2–H2chdc system, compounds 6and 7were successfully isolated, and display a zigzag chain and a helical chain, respectively. Interestingly, the cis- and trans-conformations of H2chdc were separated completely in the two compounds. The results reveal that both the coordination structure and the supramolecular assembly could be directed by the ligand isomers. Furthermore, several intriguing water clusters have been observed in these mixed-ligand compounds, such as a novel (H2O)10cluster in 2, a 2-D water net formed by (H2O)8clusters in 3, a 1-D undulated water chain in 4and a chair-shaped (H2O)6cluster in 5. The solid-state properties of compounds 1–7such as thermal stability and fluorescence have also been investigated. [ABSTRACT FROM AUTHOR]

A novel aluminum-containing, bimolybdenum-capped Keggin-type polyoxomolybate cluster of the {AlMo12O40(MoO2)2} anion has been synthesized and characterized. This is the first experimentally determined Keggin-type {AlMo12O40} polyoxoanion. The polyoxometalate crystal exhibits high selectivity toward the heterogeneous catalytic oxidation of cyclohexanol to cyclohexanone. [ABSTRACT FROM AUTHOR]

A novel copper(II) coordination polymer, poly[((aquacopper(II)]-μ3-2,2'-bipyridyl-3,3'-dicarboxylato-κ4N,N':O:O'] dihydrate], [[Cu(C12H6,N2O4)(H2O)]·2H2O]n, was obtained by the reaction of CuCl2·2H2O and 2,2'-bipyridyl-3,3'-dicarboxylic acid (H2L) in water. In the molecule, each CuII atom is five-coordinated and lies at the centre of a squarepyramidal basal plane, bridged by three L ligands to form a two-dimensional (4,4)-network. Each L moiety acts as a bridging tetradentate ligand, coordinating to three CuII atoms through its two aromatic N atoms and two O atoms of the two carboxyl groups. The two-dimensional square-grid sheets superimpose in an off-set fashion through the inorganic water layer. [ABSTRACT FROM AUTHOR]