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A nanoscale core-shell-structured magnetic microsphere (abbreviated as Fe3O4@DhaTph-lipase), which consists of an Fe3O4 core, a porphyrin covalent organic framework DhaTph shell with loaded lipase, is reported. The obtained Fe3O4@DhaTph-lipase microsphere can be a powerful emulsifier to stabilize the water-in-n-hexane Pickering emulsion for at least one month without any demulsification under ambient conditions. Furthermore, Fe3O4@DhaTph-lipase with lipase enzyme and a large specific surface area is a droplet microreactor and displays excellent interfacial catalytic activity to promote enzymatic esterification reaction via visible light-induced photothermal conversion. On the other hand, the magnetically triggered Pickering emulsion interfacial catalyst can be recycled at least 10 times with robust performance. The potential utility of this strategy is highlighted by the fabrication of many more multifunctional covalent organic framework-based Pickering emulsion catalytic systems to promote various organic transformations in a green, smart, and facile way.

Herein, we report a poly(N-isopropylacrylamide) sulfide (PNIPAM-S-) brush-tethered and Pd nanoparticle (NP) loaded UiO-66 type NMOF, namely Pd@UiO-66-S-PNIPAM, based on a NMOF–polymer covalent composite approach. The obtained multifunctional composite material can be a highly efficient Pickering emulsifier to stabilize the toluene-in-water emulsion; furthermore, it promotes the biphasic chlorobenzene (CB) dechlorination at the toluene–water interface in excellent yields at room temperature. More importantly, the Pd@UiO-66-S-PNIPAM emulsifier is thermo-responsive and can trigger emulsification at room temperature (25 °C) and demulsification at an elevated temperature (45 °C) of the toluene droplets, which makes product–catalyst in situ separation and recycling feasible. This temperature switchable Pickering emulsion catalytic system can be reused at least five times without any loss of its catalytic activity.

The substitution of base-metal oxides for noble metals is a great challenge for catalysts, sensors, and other functional materials. In this work, the dynamic structure at the interface of binary metal oxides, as a popular natural phenomenon in material science and catalysis, was studied in detail in the case of a binary copper–ceria species (CuOx-CeO2). The catalytic activity of CuOx-CeO2 could be largely improved by doping indium oxide (In2O3). The reaction rate of 1.26 × 10–5 molCO gcat.–1 s–1 for a 1.25In5Cu/CeO2 catalyst toward CO oxidation is 12 times higher than that from commercial Pd catalysts. In addition, the indium-doped catalyst shows strong resistance to CO2 and H2O poisoning. We determined the dynamic interfacial structure of CuOx/CeO2 catalysts induced by In2O3 during CO oxidation using in situ techniques, intrinsic kinetics, and density functional theory calculations (DFT). Indeed, the surface of CuOx particles could be reconstructed through the interaction with In2O3. Such an interaction ...

The determination of the dynamic active sites over binary oxide catalysts is of great challenge in heterogeneous catalysis. In this work, the origin of active sites toward low-temperature CO oxidation ( x -CeO 2 composite oxide catalysts with different Mn/Ce molar ratios, synthesized by a redox co-precipitation method. The optimum Mn 1 Ce 1 catalyst (T 100 = 190 °C), which showed excellent activity, has found to be composed of three phases: (1) CeO 2 ; (2) amorphous MnO x ; (3) MnO x -CeO 2 solid solution (active sites). With the combination of kinetics and characterization results, including Temperature-Programmed-Desorption/Reduction (TPD/TPR), operando Raman spectroscopy and in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS), the dynamic structures of catalysts were rationalized with the identification of the interface of MnO x and CeO 2 . The mechanism for CO oxidation over MnO x -CeO 2 in the temperature range 100–190 °C were proposed that the direct and the formate routes were followed at T 130 °C. Notably, the Mars-van Krevelen mechanism was proceeded in the whole temperature range. We speculate that cheap binary oxides will substitute for noble metal as catalysts for the removal of CO and other toxic gases, especially operating under mild conditions.

Iron oxychloride (FeOCl) supported on mesoporous silica (SBA-15), as a Fenton-like solid catalyst for phenol degradation, showed supreme activity for production of hydroxyl radical (HO·) by H2O2 decomposition, and the generation capacity was comparable to the conventional Fenton reagent (Fe2++H2O2). The structure of FeOCl was characterized with spectroscopies. The generation of HO· species during the reaction was detected using 5,5-dimethyl-1-pyrroline N-oxide trapped electron paramagnetic resonance. Furthermore, the kinetics in detail was driven for the creation and diffusion of HO· by H2O2 decomposition over FeOCl, which follows a first-order rate through a two-step reaction. With the combination of the catalyst structure and kinetic parameters, the plausible mechanism for H2O2 decomposition during the oxidative degradation of phenol was rationalized. As a Fenton-like solid catalyst, FeOCl/SBA-15 is a promising alternative for the removal of low-level organic contaminates from water. © 2014 American Institute of Chemical Engineers AIChE J, 61: 166–176, 2015

International audience; In this paper, we report the preparation and dielectric properties of reduced graphene oxide/polypropylene (rGO/PP) composites with an ultralow percolation threshold as low as 0.033 vol%. This value is the lowest among those that have been reported in graphene-filled composites. The rGO/PP composites were prepared through a latex technique, which consists of an in-situ chemical reduction of graphene oxide in PP latex and a subsequent filtration. Scanning electron microscopy and X-ray diffraction measurements demonstrate that the homogeneous dispersion of rGO nanosheets in the PP matrix was realized. A blue shift in Raman G band of the rGO nanosheets was observed in the rGO/PP composites, indicating the strong interaction between the rGO filler and the PP matrix. In the frequency range from 10(2) Hz to 10(7) Hz, the rGO/PP composites showed an insulator-to-conductor percolation transition as the increase of the rGO loading. Near the percolation threshold, the dielectric permittivity of the rGO/PP composites underwent a significant change of three orders of magnitude. Moreover, the permittivity was found to be temperature dependent.

Piezoresistive nanocomposites using alkyl-functionalized graphene (G-ODA) as a conducting filler and polydimethylsilicone (PDMS) as the polymer matrix were prepared and their piezoresistivity behavior was investigated. One-pot synthesis of G-ODA from graphite oxide and octadecylamine improved its dispersion in nonpolar xylene and PDMS with low surface free energy. Results show that the graphene nanosheets were homogeneously dispersed in the PDMS matrix and an ultra-low percolation threshold (0.63 vol%) of the composites was obtained. The G-ODA/PDMS composites with 1.19 vol% content of G-ODA show a remarkable positive piezoresistivity of high sensitivity (R/R0 > 400 under the pressure of 1.2 MPa), excellent repeatability, small hysteresis, and long-term durability. Under uniaxial compression, the resistance of the composites exponentially increased with the pressure. The resistance–pressure curves remain nearly unchanged after 1000 loading–unloading cycles. The results suggest that the G-ODA/PDMS nanocomposites provide a new route toward fabrication of soft piezoresistive sensors with high performance.

Tridentate Schiff base ligands L1 and L2, derived from the condensation of 2-hydroxy-3-methoxybenzaldehyde (L) with 2-aminoethanol or 2-aminobutan-1-ol, react with nickel chloride, azide, or thiocyanate to give rise to two dinuclear complexes of formulas [Ni2(L)(L1)2N3]·H2O (1), [Ni2(L2)3(μ1,1-N3)]·2H2O (2), and one tretranuclear complex [Ni2(L2)2(NCS)]2(C2H5OH)2 (3), where L1 = HOCH2CH(C2H5)NCHC6H3(O−)(OCH3) and L2 = HO(CH2)2NCHC6H3(O−)(OCH3). We have characterized these complexes by analytical, crystal structures, and variable temperature magnetic susceptibility measurements. The magnetic properties of the complexes are studied by magnetic susceptibility (χM) vs. temperature measurements. The χM T vs. T plots reveal that compounds 1, 2 and 3 are ferromagnetically coupled. Crystal of two dimers and one tetranuclear nickel (II) complexes were determined. Two dimers are azide/phenolate double bridged, and the tetranuclear is Ni4O4 cubane complex. And magnetic properties show that these compounds are ferromagnetically coupled.

The present research describes a simple low-temperature synthesis route of fabricating porous YVO4:Sm nanoplates via a chemical co-precipitation method using commercially available Y2O3, NH4VO3, Sm2O3 and ethylene glycol as the reacting precursors. The as-synthesized YVO4:Sm was thermally treated at 300°C and 600°C for 2 h which is much lower than that of the conventional preparation methods. The obtained samples were characterized by FTIR, XRD, TEM and PL. The photoluminescence measurement revealed that the luminescence intensity was significantly increased with increasing annealing temperature.

Three novel Mn(III) polymers, [Mn(phox)(2)(N(3))](n) (1), [Mn(Etphox)(2)(N(3))](n) (2), and [Mn(Etphox)(2)(C(2)N(3))](n) (3), using achiral ligand Hphox (Hphox = 2-(4,5-dihydrooxazol-2-yl)phenol) and chiral ligand HEtphox (HEtphox = 2-(4-ethyl-4,5-dihydrooxazol-2-yl)phenol) were synthesized and structurally and magnetically characterized. All complexes are of 1D chain structures and form 2D frameworks by weak interactions. The adjacent 1D chains of complex 1 are connected by face-to-face pi-pi interactions, C-H...pi interactions, and hydrogen bonding, which leads to the formation of a supramolecular 2D sheet structure. The three compounds show antiferromagnetic coupling between Mn(III) ions. And compound 2 is a spin-canted weak ferromagnet with T(N) = 5.6 K, showing metamagnetic behavior with a two-step magnetic phase transition.