Shuxia Liu

Facile Synthesis of a Nanocrystalline Metal–Organic Framework Impregnated with a Phosphovanadomolybdate and Its Remarkable Catalytic Performance in Ultradeep Oxidative Desulfurization

Reducing the level of sulfur content in fuel oils has long been desired for environmental reasons. Polyoxometalates (POMs) can act as catalysts to remove sulfur‐containing heterocyclic compounds by the process of oxidative desulfurization under mild conditions. However, one key obstacle to the development of POM‐based catalysts is the poor solubility of POMs in the overall nonpolar environment. We report a novel strategy for the introduction of catalytically active POMs into nonpolar reaction systems by encapsulating the inorganic catalyst within the pores of a metal–organic framework structure in which the organic ligands act as hydrophobic groups. The nanocrystalline catalysts, obtained rapidly and conveniently by both solution and mechanochemical synthesis, showed remarkable activities in catalytic oxidative desulfurization reactions in both a model diesel environment and in real diesel wherein dibenzothiophene was converted rapidly and quantitatively into dibenzothiophene sulfone.

Aminated Graphene Oxide Impregnated with Photocatalytic Polyoxometalate for Efficient Adsorption of Dye Pollutants and Its Facile and Complete Photoregeneration

Contamination of industrial sewage by organic dye pollutants is one of the most common challenges to the daily life. De-contamination can be achieved by adsorption and photodegradation of the pollutants. However, the former technique is generally limited by the poor loading capacity of the adsorbent and/or the difficulty in its regeneration for reuse, while the latter often suffers from sluggish reaction kinetics and thus requires long reaction time and powerful light source to be successful. Herein, a solution to these challenges by creating nanocomposites featuring porous diamine-functionalized graphene oxide (FGO) impregnated with photocatalytically active polyoxometalates (POMs) is presented. Cross-linking of GO via diamination not only generates porous structures with positively charged interior that attracts and stabilizes the anionic POM guests, but also modulates the GO bandgap. The introduction of POMs improves loading capacity of FGO for cationic dyes and promotes effective separation of electron-hole pair by trapping and transferring photogenerated electron. Thus, the two components act in synergy to result in much improved adsorption of certain common organic dyes as well as enhanced oxidative degradation by both the GO host and the POMs that lead to complete regeneration of the adsorbents without compromising their performance in multiple rounds of reuse.

An arsenicniobate-based 3D framework with selective adsorption and anion-exchange properties

An arsenicniobate-based 3D porous framework, [Cu(dap)2]4[AsNb12O40(VO)4]·(OH)·7H2O (1) (dap = 1,2-diaminopropane), was hydrothermally prepared and characterized using the IR spectrum, elemental analysis, powder X-ray diffraction, thermogravimetric analysis and X-ray single-crystal diffraction. Structural analysis shows that the framework is constructed by tetra-vanadyl capped Keggin arsenicniobate [AsNb12O40(VO)4]7− and four [Cu(dap)2]2+ linkers. The framework contains the 1D quadrangular channels of 5.7 × 5.7 A along the crystallographic c axis. The overall framework is cationic and OH− anions reside in the channels of the framework for charge balance. Considering such a structural feature, we concentrated on the probability of the framework for selective adsorption and anion-exchange. The adsorption properties show that 1 can selectively adsorb water molecules over ethanol to make them separate. Besides, anion-exchange studies for 1 suggest that the OH− anions in the channels can be quantitatively exchanged by SCN− anions.

Controllable proton-conducting pathways via situating polyoxometalates in targeting pores of a metal–organic framework

Proton conductivity is traditionally affected by proton concentration, mobility, hopping sites, etc. in metal–organic frameworks (MOFs). The influence of the profile of proton-conducting pathway has not been demonstrated due to lack of a suitable model. MIL-101 contains two types of tunnels with zigzag and linear profiles constructed by cages with different sizes. However, it is hard to construct an exclusive proton-conducting pathway with only one profile in MIL-101 because the introduced carriers usually locate without targeting a specific location. Keggin-type H3PW12O40 (HPW) has a unique nano size, which is between the window sizes of the cages in MIL-101, strong acidity, good stability, and abundant proton-hopping sites. Herein, two types of hydrogen bond networks were constructed by situating HPWs in the targeting pores of MIL-101. Linear pathways provide about 2.1-fold faster proton diffusion rates compared to zigzag pathways. Further modification of an HPW-impregnated MIL-101 with flexible polyamine resulted in a conductivity of 1.52 × 10−2 S cm−1.

Calcitonin promotes mouse pre-implantation development: involvement of calcium mobilization and P38 mitogen-activated protein kinase activation.

The study was designed to examine the effects of calcitonin (CT) on the development of murine pre-implantation embryos and possible molecular mechanisms involved in the process. In the present study, the 2-cell embryos were treated with different concentration of CT in vitro for the indicated time and the results demonstrated that CT promoted the development of the pre-implantation embryos in a dosage-dependent manner by increasing the intracellular Ca(2+) level. Furthermore, the present study showed that CT significantly increased the expression of phospho-P38MAPK (Mitogen-Activated Protein Kinase) of the pre-implantation embryos by Western blots and pre-treatment of specific P38MAPK inhibitor significantly reduced the promotion effects of CT on the embryonic development in vitro culture. Moreover, the results of intrauterine horn injection showed that the average number of embryos implanted in CT-antibody or specific P38 MAPK inhibitor-treated uterus was significantly lower than that of the corresponding control, respectively. And the observation of tissue specimen suggested that some embryos were degenerated in CT-antibody or specific P38 MAPK inhibitor-treated uterus, and adipose vacuoles were present in the decidual cells. In conclusion, CT promoted the development of pre-implantation embryos and the intracellular Ca(2+) -dependent P38MAPK signal molecule was involved in the process.

Magnetic and luminescence properties of an inorganic 3D nickel-vanadium bimetallic framework

A novel nickel–vanadium bimetallic compound [Ni(H2O)2V2O6] (1) has been hydrothermally prepared and characterized by IR spectroscopy, elemental analysis, powder X-ray diffraction, thermogravimetric analysis, and X-ray single-crystal diffraction. Compound 1 exhibits an interesting purely inorganic 3D framework with a pair of entangled double helices, constructed by a {NiO4(H2O)2} octahedron and a {VO4} tetrahedron arranged alternately to each other. The magnetic behavior demonstrates the antiferromagnetic interactions transmitted by a pair of O–V–O bridges. Besides, luminescence measurements exhibit an intense broad emission maximum at λ ≈ 525 nm owing to the O → V charge transfer within the {VO4} groups.

Trisodium bis-{1-[iminio-(morpholino)meth-yl]guanidinium} bis-[hexa-hydrogen-hexa-molybdoaluminate(III)] chloride icosa-hydrate.

In the title compound, Na3(C6H15N5O)2[Al(OH)6Mo6O18]2Cl·20H2O, the [Al(OH)6Mo6O18]3− polyoxoanion has a B-type Anderson structure exhibiting approximate D 3d symmetry. There are two types of sodium cations: the Na+ cations of type I have a distorted octahedral coordination geometry formed by six O atoms and are statistically distributed over two positions with equal occupancies, while the coordination polyhedra of the two Na+ cations of type II share one Cl anion located on an inversion center. The latter fragment, containing a Cl anion and two sodium cations, links two polyoxoanions into centrosymmetric blocks. The diprotonated 1-[imino(morpholino)methyl]guanidinium cations and uncordinated water molecules contribute to extensive N—H⋯O and O—H⋯O hydrogen bonding, resulting in the formation a three-dimensional supramolecular structure.

Bis(amino{[iminio(morpholino)methyl]amino}iminium) bis(amino{[imino(morpholino)methyl]amino}iminium) tetracosaoxidotellurohexamolybdate(6−) tetrahydrate

The title compound, (H2ABOB)2(HABOB)2[TeVIMoVI6O24]·4H2O, consists of an Anderson-type heteropolyanion, [TeVIMoVI6O24]6−, two monoprotonated ABOB cations, two diprotonated ABOB cations and four water molxadecules (ABOB = N-amidino-4-morpholincarboxamidine). The heteroxadpolyanion [TeVIMoVI6O24]6− is located on an inversion center. Electrostatic forces and hydrogen-bonding interxadactions among the [TeVIMoVI6O24]6−anions, the water molxadecules and the ABOB cations result in a three-dimensional supraxadmolecular structure.

Synthesis and properties of a POM-based trinuclear copper(II) triazole framework

A novel POM-based trinuclear copper(II) triazole framework, namely, [H2{Cu6(trz)6(μ3-OH)2}Mo5O18]·3H2O (1) was isolated using a hydrothermal method, which displays a 3D network constructed from trinuclear copper(II) units and triazole ligands with [Mo5O18]6− anions as templates. 1 has been identified by single crystal X-ray diffraction, elemental analysis, thermogravimetric analysis, powder X-ray diffraction and FT-IR. Magnetic studies indicate that antiferromagnetic interactions exist in 1. In addition, 1 exhibits good Lewis acid catalytic activity for the synthesis of cyclohexanone ethylene ketal with 95% conversion. The HOMO–LUMO gap (Eg) of 1 is 2.34 eV calculated using the Kubelka–Munk equation (Fhν)0.5, indicating that its forbidden bandwidth belongs to the semiconductor category. Visible-light photodegradation of RhB catalyzed by 1 was investigated, which shows high activity with an above 98% degradation rate.

A gel-like/freeze-drying strategy to construct hierarchically porous polyoxometalate-based metal–organic framework catalysts

Hierarchically porous metal–organic frameworks combining the merits of micropores with high surface areas and mesopores/macropores with large diffusion channels are highly desired in catalysis, especially for reactions involving large substrates. In this work, a simple and common solvent templating strategy for the construction of hierarchically micro- and mesoporous polyoxometalate-based metal–organic frameworks by a gel-like/freeze-drying method was achieved. Fast nucleation and interconnection of nanoparticles with micropores were realized in the gel-like stage. Subsequently, the synthesized mesopores were strengthened by the squeezing by ice crystals due to volumetric swelling during the process of freezing water into ice. The hierarchically porous material showed improved catalytic activities for the oxidation of alcohols compared to the catalyst without hierarchical pores, due to it having more easily accessible catalytic sites and the acceleration of mass transfer.