Shuiying Gao

An Anion Metal–Organic Framework with Lewis Basic Sites-Rich toward Charge-Exclusive Cationic Dyes Separation and Size-Selective Catalytic Reaction

Organic dye pollutants become a big headache due to their toxic nature to the environment, and it should be one of the best solutions if we can separate and reuse them. Here, we report the synthesis and characterization of a microporous anion metal-organic framework (MOF) with Lewis basic sites-rich based on TDPAT (2,4,6-tris(3,5-dicarboxylphenylamino)-1,3,5-triazine) ligand, FJI-C2, which shows high adsorption and separation of cationic dye based on the charge-exclusive effect. Compared to other MOF materials, FJI-C2 shows the largest adsorption amount of methylene blue (1323 mg/g) at room temperature due to the nature of the anion frameworks and high surface area/pore volume. Furthermore, motivated by the adsorption properties of large guest molecules, we proceeded to investigate the catalytic behaviors of FJI-C2, not only because the large pore facilitates the mass transfer of guest molecules but also because the high density of Lewis basic sites can act as effective catalytic sites. As expected, FJI-C2 exhibits excellent catalytic performance for size-selective Knoevenagel condensation under mild conditions and can be reused several times without a significant decrease of the activity.

Photocatalytic property of a keggin-type polyoxometalates-containing bilayer system for degradation organic dye model

The photocatalytic activity composite films incorporating the Keggin-type polyoxometalates (POM) K6CoW12O40.-16H2O and K3PW12O40.-nH2O (MW12 (M=P, Co)) and [Cu(II)(1,8-dimethyl-1, 3, 6, 8, 10, 13-hexaazacycloteradecane)](2+)(L) have been prepared by the layer-by-layer (LbL) self-assembly method. The experimental results show that the deposition process is linear and highly reproducible from layer to layer. Atomic force microscopy (AFM) images of the L/MW12 composite films indicate that the film surface is relatively uniform and smooth. In addition, the films show high photocatalytic activity to the degradation of organic dye model (methyl orange (MO)), attributed to the formation of an O-->W charge-transfer excited state at W-O-W bridge bond, resulting in generating highly reactive holes and electrons; The photocatalytic efficiency of the films have little change after several times of photocatalytic cycle, indicating that the composite films are stable, reused and recovered.

Electrochemical preparation of metal–organic framework films for fast detection of nitro explosives

A facile electrochemical plating method by means of applying voltage onto zinc electrodes in a 1,3,5-benzenetricarboxylic acid (H3BTC) electrolyte has been developed to prepare fluorescent MOF films (Zn3(BTC)2). The composition of as-prepared MOF films is confirmed by powder X-ray diffraction (PXRD) and the surface morphology is examined by scanning electron microscopy (SEM). Voltage and fabrication time are found to be the key parameters for the formation and morphology control of MOF films. Additionally, the as-prepared MOF films, due to their evident fluorescence, are explored for potential applications in detecting nitro explosives with a detection limit as low as 0.5 ppm. The fluorescent MOF films can be further applied to distinguish nitro explosives by varying the solution concentration. Moreover, the MOF films exhibit excellent reusability in consecutive nitro explosive detection reactions. It has been demonstrated that the electrochemical plating method reported here offers a reliable and efficient way to prepare MOF films with controllable morphology for nitro explosive detection.

In Situ Growth of Metal–Organic Framework Thin Films with Gas Sensing and Molecule Storage Properties

New porous metal-organic framework (MOF) films based on the flexible ligand 1,3,5-tris[4-(carboxyphenyl)oxamethyl]-2,4,6-trimethylbenzene (H3TBTC) were fabricated on α-Al2O3 substrates under solvent thermal conditions. The factors affecting the fabrication of films, such as the temperature of pre-activation and the dosage of the reagents, were investigated. Tuning the subtle factors on film fabrications, a series of MOF thin films with different morphologies and grain sizes were prepared. The morphology and grain size of the films are monitored by scanning electron microscopy (SEM). X-ray diffraction (XRD) and attenuated total reflection infrared (ATR-IR) were also used to characterize the MOF films. The results indicate that the temperature of pre-activation and the dosage of the reagents are the key parameters during the process of film formation. The properties of the films, especially the sensing and sorption behavior, have been studied by an optical digital cameral and ultraviolet-visible (UV-vis) spectra. The evidence shows that the films are sensitive to small organic molecules, such as methanol and pyridine. Meanwhile, the films can adsorb small dye molecules. Thus, the films may have potential applications in either organic vapor sensing or storage of small dye molecules.

Platinum Nanoparticles Stabilized by Cucurbit[6]uril with Enhanced Catalytic Activity and Excellent Poisoning Tolerance for Methanol Electrooxidation

Three sub-10 nm platinum nanoparticles (PtNPs) with distinctive morphologies were developed by using cucurbit[6]uril (CB[6]) as stabilizing agent and support. Both the size and shape of the PtNPs were simultaneously controlled by tuning the reducing agents. The prepared NPs have been comprehensively characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and cyclic voltammetry. On account of the presence of CB[6] and its unique structural features, the as-prepared PtNPs are homogeneous in morphologies and exhibit higher activities toward methanol electrooxidation than commercial Pt/C. CB[6] has the ability to bind small molecules that can promote CO oxidation, therefore, all the three PtNPs showed enhanced poisoning tolerance. Such unique abilities of CB[6] can even promote the poisoning tolerance of commercial Pt/C through simple physical mixing.

Progressive release of a palladium-pyridyl complex from a layer-by-layer multilayer and illustrative application to catalytic Suzuki coupling

Quartz slides bearing layers of a palladium azopyridine complex are seen to liberate catalytic amounts of a soluble active palladium species which can be used for Suzuki coupling.

[Zn2(H2O)3(2,2′-bipy)2(btc)][Zn(H2O)(2,2′-bipy)(btc)] ·8H2O: a novel zinc–carboxylate complex consisting of independently cationic and anionic chains

A novel zinc complex, [Zn 2 (H 2 O) 3 (2,2 ′ -bipy) 2 (btc)][Zn(H 2 O)(2, 2 ′ -bipy)(btc)]·8H 2 O ( 1 ), (H 3 btc=1,3,5- benzenetricarboxylic acid, 2,2 ′ -bipy=2,2 ′ -bipyridine) has been prepared by hydrothermal reaction of H 3 btc, Zn(CH 3 CO 2 ) 2 ·2H 2 O and 2,2 ′ -bipyridine at 180 °C and characterized by single-crystal X-ray diffraction analysis. Complex 1 consists of independently cationic and anionic chains. The hydrogen bonding interactions between chains extend 1 into a two-dimensional supramolecular architecture.

Dye–polyoxometalate composite films: Self-assembly, thermal and photochemical properties

A series of dye-polyoxometalate composite films were prepared by alternately depositing cationic dye molecules and anionic polyoxometalates such as Keggin-type [BW(12)O(40)](5-) and the sandwich complex [Co(4)(H(2)O)(2)(PW(9)O(34))(2)](10-)via layer-by-layer (LbL) self-assembly method. These cationic dye molecules (MB, AA, TH, BB3, BCB and NB) are heterocyclic planar and rigid phenothiazine and phenoxazine dye molecules with different substituting groups in the side chains. The self-assembly of the films was studied by UV-vis and IR spectra. The results show that the substituting groups of dye molecules such as NH(2) and CH(2)CH(3) have influence on the self-assembly properties. The continuous and regular growth of the films was also dependent upon hydrogen bonding (NHO) formed between the amino groups of dye molecules and oxygen atoms of POMs as well as electrostatic interactions. The investigation of thermal and photochemical treatments of the composite films is also presented. The thermal stability experiments indicate that the composite films of TH with two NH(2) substitute groups and NB with more pi-conjugated system exhibit high thermal stability, whereas the sunlight irradiation results indicate that the composite films of TH have good photochemical stability.

Synthesis of palladium nanocatalysts with cucurbit[n]uril as both a protecting agent and a support for Suzuki and Heck reactions

Pd nanocatalysts based on cucurbit[n]uril were successfully synthesized by an operationally simple one-pot liquid-phase method using different reducing agents. Through changing the reducing agents and the ratio of feedstock, well-defined Pd nanostructures with various shapes were obtained. The results of morphological analysis demonstrate that cucurbit[6]uril plays a key role in guiding the formation of Pd nanostructures, and is responsible for the Suzuki and Heck coupling reactions with high efficiency.

Photocatalytic properties of polyoxometalate–thionine composite films immobilized onto microspheres under sunlight irradiation

Multilayer films (PW12–TH)n (PW12 = PW12O403−, TH = thionine) were prepared on quartz slides and MnCO3 microspheres by an electrostatic layer-by-layer (LbL) self-assembly method. The composite films on quartz slides were characterized by UV-vis spectra and atomic force microscopy (AFM) images. MnCO3 microspheres coated with (PW12–TH)n composite films were characterized by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. The microspheres exhibited photocatalytic activity for methyl orange (MO) under sunlight irradiation. Compared with the (PW12–TH)10 composite films on quartz slides, the microspheres showed a higher photoactivity due to the increase of the specific surface area. The photocatalytic properties of the microspheres toward a rhodamine B (RhB) solution were also investigated. The results indicated that the decrease of the absorbance was due to the destruction of the dye chromophore. The kinetics of the photodecomposition follows the first-order reaction. The dye molecule TH of the composite films is excited by sunlight irradiation to the appropriate excited states. Then, the electron injection into the conduction band of polyoxometalates (POMs) follows and results in the photodegradation of the target dye molecules.