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Sun W.,Hunan Normal University | Tan R.,Hunan Normal University | Zheng W.,Hunan Normal University | Yin D.,Hunan Normal University | Yin D.,China Tobacco Hunan Industrial Corporation
Cuihua Xuebao/Chinese Journal of Catalysis | Year: 2013

A series of molecularly imprinted polymers (MIPs) containing equal amounts of iron(III) were prepared by the polymerization of acrylamide and ethylene dimethacrylate in the presence of the template of o-, m-, or p-nitrobenzyl alcohol (NBA) and a FeCl3 complex. The samples were characterized by scanning electron microscopy, N2 adsorption, and Fourier transform infrared spectroscopy. The catalysts exhibited high catalytic activity and unique substrate recognition in the oxidation of benzyl alcohol derivatives in water using 30% H2O2 as the oxidant. The conversion of p-NBA was 80% over the p-Fe(III)-MIP catalyst when the template molecule was p-NBA, which had a good fit with the substrate. However, the conversion of p-NBA was less than 58% over o-Fe(III)-MIP or m-Fe(III)-MIP due to the mismatch of the substrate with the cavities of the Fe(III)-MIP. The results indicated that the Fe(III)-MIP samples contained molecular recognizable shapes and sites in their cavities that match the corresponding substrate. The special recognizing cavities of the Fe(III)-MIP catalyst exhibited unique substrate recognition, and therefore the selectivity for the substrate was improved. © 2013, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Zeng J.-L.,Changsha University | Zhu F.-R.,Changsha University | Yu S.-B.,China Tobacco Hunan Industrial Corporation | Zhu L.,Changsha University | And 5 more authors.
Solar Energy Materials and Solar Cells | Year: 2012

The effects of copper nanowires (Cu NWs) with ultra-high aspect ratio and sponge-like structure on the properties of an organic phase change material (PCM) were investigated. Tetradecanol (TD) was selected as the organic PCM. The sponge-like Cu NWs clusters were randomly dispersed in the TD matrix and were wrapped by TD to form a new kind of composite PCM. The phase change enthalpy (ΔH) of the composite PCMs was decreased linearly with the increasing of Cu NWs loading, while the melting speed was accelerated. The thermal conductivity of the composite PCMs was greatly enhanced by Cu NWs. The ΔH of the composite PCM containing 58.9 wt% (corresponding to 11.9 vol%) of Cu NWs was 86.95 J/g, and the thermal conductivity attained to 2.86 W/m K, which was nearly 9 times higher than that of the TD. The thermal conductivity enhancement of Cu NWs on the composite PCMs showed a turning point at the Cu NWs loading of 1.5 vol%. When Cu NWs loading exceeded 1.5 vol%, the thermal conductivity of the composite PCMs increased significantly faster with the increasing of Cu NWs loading. © 2012 Elsevier B.V.

Tan R.,Hunan Normal University | Li C.,Hunan Normal University | Luo J.,Hunan Normal University | Kong Y.,Hunan Normal University | And 3 more authors.
Journal of Catalysis | Year: 2013

Pristine l-proline was non-covalently loaded on the graphene oxide (GO) sheet in a simple route by mixing them in aqueous solution. Technologies of characterization well suggested that l-proline was efficiently loaded on the two sides and edge of the GO sheet through hydrogen-bonding or/and ionic interaction, giving the excellent l-proline/GO hybrid catalyst for the direct asymmetric aldol reaction. The unique multilayered structure of the GO carrier with sufficient interlayer space favored reagents' diffusion toward l-proline chiral moiety and therefore resulted in the high catalytic efficiency of the heterogeneous l-proline. Excellent yield (96%) with high enantiomeric excess (79% ee) was obtained in the direct aldol reaction of 2-nitrobenzaldehyde with acetone catalyzed by l-proline/GO hybrid, which was comparable to that observed in the reactions promoted by l-proline itself. Furthermore, the l-proline/GO hybrid used as a heterogeneous catalyst could be easily recovered and recycled for seven times without significant loss of the reactivity. © 2012 Elsevier Inc. All rights reserved.

Tan R.,Hunan Normal University | Dong Y.,Hunan Normal University | Peng M.,Hunan Normal University | Zheng W.,Hunan Normal University | And 2 more authors.
Applied Catalysis A: General | Year: 2013

A series of novel chiral salen Mn(III) complexes possessing a thermoregulated phase-transfer function was prepared for the first time. The preparation involved the introduction of the "smart" poly(N-isopropylacrylamide) (PNIPAAm) group to the framework of the chiral salen Mn(III) complex by covalently connecting to one side of the 5-position in the salen ligand (complex 1) or by axially grafting onto the metal center of the complex (complex 2). Characterization results suggested the presence of the PNIPAAm moiety and active sites in the complexes. The thermoresponsive PNIPAAm groups imparted inverse temperature-dependent water solubility to the PNIPAAm-based complexes, which allowed them to undergo thermoregulated phase-separable catalysis during oxidative kinetic resolution (OKR) in water. Excellent enantioselectivity (up to 96%) with high kinetic resolution efficacy (13.1) was achieved over complex 1 in the aqueous OKR of α-methylbenzyl alcohols, and this efficacy was significantly higher than that obtained over neat complex. The PNIPAAm-based complexes can also be easily recovered by simply regulating the temperature and be reused for four times without obvious loss of enantioselectivity and activity. © 2013 Elsevier B.V. All rights reserved.

Kong Y.,Hunan Normal University | Tan R.,Hunan Normal University | Zhao L.,Hunan Normal University | Yin D.,Hunan Normal University | Yin D.,China Tobacco Hunan Industrial Corporation
Green Chemistry | Year: 2013

Grafting l-proline on imidazolium-based ionic liquid (IL)-functionalized magnetic nanoparticles afforded a magnetically recoverable l-proline catalyst. Characterization technologies suggested the presence of an l-proline backbone, an IL linker, and a magnetic ferrite core in the catalyst. The resulting l-proline catalyst was efficient for direct asymmetric aldol reaction in water without the need for organic solvents and co-catalysts. Such efficiency is attributed to the fact that the IL moiety facilitated the accessibility of hydrophobic reactants to active sites in water and stabilized the formed enamine intermediate during the reaction. High activity (yield = 92%), diastereoselectivity (dr; 88/12) and enantioselectivity (ee; 85%) were obtained using 10 mol% of a catalyst for the reaction between cyclohexanone and 2-nitrobenzaldehyde within 12 h, where the pristine l-proline and IL-free counterpart were almost inactive. The catalyst was easily separated using a permanent magnet externally and can be reused several times without significant loss of activity. © 2013 The Royal Society of Chemistry.

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