Assembly of Lanthanide-Containing 3D [MnMo9O32]6--Based Metal-Organic Frameworks and Oxidative Desulfurization Performance.

Lanthanide-containing polyoxometalate-based metal-organic frameworks (POMOFs) not only enjoy intriguing architectures but also have good application prospects as catalysts. Herein, three novel three-dimensional (3D) POMOFs with the formulas of {H[Ln3(2,6-pydc)2(H2O)10(MnMo9O32)]·2H2O}n (Ln = La(1), Pr(2), Nd(3)) have been synthesized based on Waugh-type [MnMo9O32]6- anions and pyridine-2,6-dicarboxylate (2,6-H2pydc). Compounds 1-3 are isomorphic, and there are two kinds of one-dimensional (1D) helical chains with opposite handedness staggered into two-dimensional (2D) layers. Interestingly, the coordinated L- and R-[MnMo9O32]6- anions are encapsulated in 1D chains with the same chirality and are further expanded into 3D structures. The catalytic tests indicate that compounds 1-3 exhibit high-efficiency heterogeneous catalytic activity in the oxidative desulfurization reaction for catalyzing the oxidation of sulfides to sulfoxides using tert-butyl hydrogen peroxide (TBHP) as the oxidant. Moreover, a series of control experiments have been conducted to investigate the influence of various parameters such as temperature, time, solvent, catalyst, and substrate on the reaction. Significantly, compound 2, as an example, exhibits good reusability and structural stability in the oxidative desulfurization reaction. It is worth noting that investigations on the oxidative desulfurization of [MnMo9O32]6- anions are scarce. Moreover, their electrochemical properties are also explored.

Design and Synthesis of Amphiphilic Catalyst [C16mim]5VW12O40Br and Its Application in Deep Desulfurization with Superior Cyclability at Room Temperature.

Achieving long-term stable deep desulfurization at room temperature and recovering high value-added sulfone products is a challenge at present. Herein, a series of catalysts [Cnmim]5VW12O40Br (CnVW12, 1-alkyl-3-methylimidazolium bromide tungstovanadate, n = 4, 8, 16) were presented for the room temperature catalytic oxidation of dibenzothiophene (DBT) and its derivatives. Factors affecting the reaction process, such as the amount of catalyst, oxidant, and temperature, were systematically discussed. C16VW12 showed higher catalytic performance, and 100% conversion and selectivity could be achieved in 50 min with only 10 mg. The mechanism study showed that the hydroxyl radical was the active radical in the reaction. Benefiting from the "polarity strategy", the sulfone product accumulated after 23 cycles in a C16VW12 system, and the yield and purity were about 84% and 100%, respectively.

Two three-dimensional Fe(II) frameworks based on {P4Mo6} tetrameric clusters exhibiting efficient visible-light photocatalytic properties for the degradation of Cr(VI) and methylene blue.

Two three-dimensional frameworks based on the {P4Mo6} unit, H(4,4'-bipy)2[Fe4(PO4)(H2O)4Na6][Fe6(H2O)4][(Mo6O12)(HPO4)3(PO4)(OH)3]4·5H2O (4,4'-bipy = 4,4'-bipyridine) (1) and H3(C12H14N2)4[Fe4(PO4)(H2O)4Na4][Fe2(Mo6O12(HPO4)3(PO4)(OH)3)4]·6H2O (2) were successfully synthesized by varying the solvent. The extended structures of the two compounds were formed by transition metal Fe(II) ions bridging the {P4Mo6}-based tetrameric clusters around [NaXFe4(PO4)] (X = 6 (1), or X = 4 (2)) core. The 4,4'-bipy molecules and in situ generated methyl viologen cations as templates induce the formation of two three-dimensional structures, an 8-connected bcu topology framework for 1 and a 4-connected 2-fold interpenetrating diamond-like topological network for 2, respectively. Additionally, multiform hydrogen bonds are found in the framework and also play an important role in stabilizing the structure. The proton conduction mechanism of the two compounds can be mainly classified as the Grotthuss mechanism; the proton conductivity values are 1.06 × 10-3 S cm-1 for 1 and 3.13 × 10-3 S cm-1 for 2 at 75 °C under 98% relative humidity. The visible-light photocatalytic activity was evaluated by photocatalytic decomposition of Cr(VI) and MB dye, and the removal ratios can reach 95.6% (1) and 82% (2) for Cr(VI), and 98% (1) and 99% (2) for MB.

Progress in Pretreatment and Analytical Methods of Coumarins: An Update since 2012 - A Review.

Coumarins are widely used due to their wide range of biological activities, but the long-term or excessive use of coumarin flavors can pose serious health hazards. Therefore, sensitive and specific methods for the quantification of these compounds in different matrices have been developed. In this review, an updated overview of the latest trends in sample preparation techniques and methods used to detect coumarins from March 2012 to April 2019 is provided. This study reviews different analytical methods (such as liquid chromatography coupled with different detectors, electrochemical sensors, capillary electrophoresis, etc.) and different pretreatment methods (such as liquid-liquid extraction, solid-phase extraction, dispersive liquid-liquid microextraction, etc.). Different methods for the pretreatment and determination of coumarins in plant, food, environmental, pharmaceutical and biological samples are summarized, discussed and compared.HighlightsProgress in pretreatment and analytical methods of coumarins are summarized.Fundamentals, instrumentation and applications of purification and quantification are summarized and compared.Optimization of experimental conditions are discussed.Newly emerged eco-friendly methods are introduced.

Three-Dimensional Interpenetrating Frameworks Based on {P4Mo6} Tetrameric Clusters and Filled with In Situ Generated Alkyl Viologens.

Four novel three-dimensional interpenetrating frameworks based on {P4Mo6} units, H[C12H14N2]4[TM4(PO4)(H2O)4Na6][TM2(Mo6O12(HPO4)3(PO4)(OH)3)4]·8H2O (1, 2) and H[C14H18N2]4[TM4(PO4)(H2O)4Na6][TM2(Mo6O12(HPO4)3(PO4)(OH)3)4]·8H2O (3, 4) (TM = Co2+ (1, 3), Mn2+ (2, 4)) were synthesized and characterized using infrared spectroscopy, elemental analyses, thermogravimetric analysis, and single-crystal X-ray diffraction. In situ generated methyl viologen (compounds 1 and 2) or ethyl viologen (compounds 3 and 4) cations function as templates to induce the generation of 2-fold interpenetrating structures in which the {P4Mo6} tetrameric clusters with [TM4(PO4)Na6] (TM = Co2+ (1, 3) and Mn2+ (2, 4)) as the core were bridged by transition metal ions. Compounds 1-4 possess high thermal stabilities and the decomposition temperature of the inorganic frameworks were all >500 °C. It is worth noting that the four compounds all exhibited the bifunctional catalytic performance that they not only had an excellent photocatalytic activity for the reduction of hexavalent chromium (Cr(VI)) under visible light irradiation but also showed a good electrocatalytic activity for the reduction reaction of hydrogen peroxide.

Ionothermal Synthesis of an Antimonomolybdate Cluster, [Sb8MoVI13MoV5O66]5-, and Its Catalytic Behavior to the Reduction of Nitrobenzene.

The largest antimonomolybdate monomer, [Sb8MoVI13MoV5O66]5- (1-Sb8Mo18), has been isolated and displays a new breakthrough of polyoxometalates (POMs) with an ionothermal synthesis strategy. 1-Sb8Mo18 features the first hexanuclear sandwich-type polymolybdate (POMo) with an unexpected metal ring {Sb6O12} to make its debut in Sb clusters. Furthermore, 1-Sb8Mo18 exhibits a prominent catalytic activity for reducing nitrobenzene to aniline with excellent sustainability.

[Optimal protocol of MR contrast imaging in diabetic foot].

OBJECTIVE: To identify the optimal protocol of MR contrast imaging in diabetic foot. METHODS: 20 patients with diabetic feet were enrolled and examined with 3D FLASH-MRA, 3D VIBE-WE, 2D SE-FS, 2D TSE-FS and 2D FLASH-FS at a 1.5T MR scanner for vascular changes in feet. Their effectiveness in displaying blood vessels, venous aliasing and articular cartilage, as well as the signal-to-noise ratio (SNR) and contrast ratio (CR) of plantar skins calcaneus, flexor digitorum brevis, dorsal artery, and talocalcaneal joint cartilage in diabetic feet were compared. RESULTS: (1) 3D FLASH-MRA was better in displaying blood vessels and venous aliasing than the others (P < 0.05); (2) 3D VIBE-WE was better in displaying articular cartilage than 2D SE-FS, 2D TSE-FS and 2D FLASH-FS (P < 0.05); (3) 3D VIBE-WE had higher SNR and CR of plantar skins, dorsal artery, talocalcaneal joint cartilage, calcaneus, and flexor digitorum brevis than the others (P < 0.05). CONCLUSION: 3D VIBE-WE is the preferred sequence for T1 weighted imaging with contrast in diabetic feet. It can also serve as the supplemental sequence of 3D FLASH-MRA in MR angiography.

[Role of Fas/FasL on apoptosis of porcine follicular granulosa cells derived from isolated follicles during culture in vitro].

The whole antral follicles were isolated from porcine ovaries and classified as follows: healthy follicles (HF), early atretic follicles (EF) and progressed atretic follicles (PF). The isolated porcine follicles were used for routine histological section and HE staining after examination by eyesight. Morphological research shows that the accuracy rate of eyesight examination for HF is 92%. Healthy follicles were chosen for further experiment and divided into 3 groups: large follicles (greater than 5 mm in diameter), medium follicles (3-5 mm in diameter) and small follicles (less than 3 mm in diameter). All follicles were cultured for 8, 16 and 24 h, respectively and the apoptosis of of their granulosa cells were examined by Annexin V-FITC/PI double-labeling. It showed that the total apoptotic rate of granulosa cells derived from cultured follicles could reach over 70% at 8 h after culture and be 81.1% - 94.6% at 24 h after culture. Granulosa cells from groups were collected at 0, 8, 16, 24, 48 and 72 h after culture without serum and used for the examination of expression of FasL and Fas mRNA with real time PCR SYBRgreen method. The expression level of FasL mRNA of granulosa cells from different size of follicles increased with culture time and reached the highest level at 24 h after culture (P<0.05). Expression level of FasL mRNA of granulosa cells from small follicles was higher than those from large and medium follicles. There exists no difference for expression level of Fas mRNA of granulosa cells among groups before culture but significantly increased at 8 h after culture and reached the highest level at 48 h after culture. It showed in the present experiment that the follicular culture system without serum used could effectively induce the apoptosis of follicular granulosa cells. Cell apoptosis is the main cause of follicular atresia, the degree of which varied with the size of follicles. Small follicles seemed to be easier atretic than medium and large follicles.