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  • Design and generation of extended zeolitic metal-organic frameworks (ZMOFs)

    • 摘要:

      Attempts to create metal-organic frameworks (MOFs) with zeolitic topologies, metal (zinc(II) and cobalt(II)) imidazolates have repeatedly been used as the metal-organic motifs of inorganic silicate analogues. By modulating the synthetic strategy based on the solvothermal and liquid diffusion method, seven further MOFs (including at least three zeolitic MOFs) of zinc(II) imidazolates, [Zn(im)2·x G] (G=guest molecule, x = 0.2-1) 1a-7a, have been successfully synthesized. Of these, 1a-3a are isostructural with the previously reported cobalt analogues 1b-3b, respectively, while 4a-7a are new members of the metal imidazolate MOF family. Complex 4a exhibits a structure related to silicate CaAl2Si2O8 of CrB4 topology, but with a higher network symmetry; complex 5a has a structure with zeolitic DFT topology that was discovered in zeolite-related materials of DAF-2, UCSB-3, and UCSB-3GaGe; complex 6a demonstrates an unprecedented zeolite-like topology with one dimensional channels with 10-rings; and 7a displays a structure of natural zeolite GIS (gismondine) topology. All of these polymorphous MOFs were created only by using certain solvents as structure-directing agents (SDAs). Further extensive metal-organic frameworks with zeolitic topologies can be envisaged if other solvents were to be used.

    • 作者:

      Yun Qi Tian;Yu Ming Zhao;Zhen Xia Chen;Guang Ning Zhang;Lin Hong Weng;东元 赵

    • 刊名:

      Chemistry - A European Journal

    • 在线出版时间:

      2007

  • Siliceous mesostructured cellular foams with uniformly sized and shaped pores

    • 摘要:

      Mesostructured siliceous cellular foams (mesocellular foams, MCFs) with homogeneous ultra-large mesopores are described. MCFs consist of uniform spherical cells 21-36 nm in diameter and possess surface areas up to 900 m2/g. Uniform windows, 7-18 nm in diameter, interconnect the cells to form a continuous 3-D pore system, which makes the MCFs attractive candidates for supports for catalysis and in separation and immobilization involving large molecules. They may be of interest in low-dielectric applications. The size of the cells can be controlled by the concentration of the added organic cosolvent. Adding small amounts of NH4F selectively enlarges the windows. We propose that the MCFs are templated by oil-in-water microemulsion droplets. The large-pore MCF materials resemble aerogels, with the benefit of a facilitated synthesis procedure in combination with well-defined pores and wall structure.

    • 作者:

      P. Schmidt-Winkel;W. W. Lukens;东元 赵;P. Yang;B. F. Chmelka;G. D. Stucky

    • 刊名:

      Materials Research Society Symposium - Proceedings

    • 在线出版时间:

      1999

  • Nano-spatially confined Pd-Cu bimetals in porous N-doped carbon as an electrocatalyst for selective denitrification

    • 摘要:

      Bimetals have attracted considerable attention as electrocatalysts towards selective reduction of nitrate to benign dinitrogen. Design of highly efficient and stable bimetallic catalysts by taking the effects of both active sites increasing and synergistic composition into account is of paramount importance but still a grand challenge. Herein we report novel bimetallic Pd-Cu nanoparticles (NPs) incorporated in porous N-doped carbon octahedra prepared by a spatial confinement strategy ofin situpyrolysis of metal-organic frameworks with the assistance of polyvinyl pyrrolidone (PVP) as electrocatalysts achieving targeted denitrification. Pd-Cu NPs exhibit superior dispersity with a N-doped matrix and are strongly dependent on the variation of PVP, Pd precursor and pyrolysis temperature. The material shows high efficiency (~97.1%) for the reduction of nitrate from 100 to 2.9 mg NO3--N L-1(well below drinking water standards of 10 mg NO3--N L-1), and especially the selectivity over 83% for benign N2at neutral pH within 24 h. Encapsulated and well-dispersed Pd-Cu NPs and doped N in the carbonaceous matrix synergistically enhance the interfacial electron transfer for transformation of NO3--N(v). Porous structures endow the catalyst with outstanding stability after eight cycles and over a wide pH of 4-10. More importantly, the nanocatalyst performs well with real contaminated water (selectivity of 91% for nitrogen) in laboratory batch reactors. This nanocatalyst shows promise in wastewater treatment and environmental remediation due to the spatial confinement strategy and introduction of heterogeneous atoms.

    • 作者:

      Tianhang Gu;Wei Teng;Nan Bai;Zehan Chen;Jianwei Fan;Wei Xian Zhang;东元 赵

    • 刊名:

      Journal of Materials Chemistry A

    • 在线出版时间:

      2020-5-21

  • Graphitic N-free/N-doped Nanostructured carbon molecular sieves via CVD method and their hydrogen storage

    • 摘要:

      Graphitic N-free and N-doped carbon molecular sieves were prepared using zeolite NaY as a template via one-step chemical vapor deposition method (CVD) with propylene and acetonitrile as N-free and N-doped carbon precursors, respectively. The morphology, structure and properties of the carbons prepared were characterized via XRD, SEM, TEM and adsorption measurements. A large proportion of pore volume is associated with micropores in the carbons prepared. A high hydrogen uptake capacity is observed.

    • 作者:

      Chun Xia Zhao;Yun Xia Yang;Wen Chen;东元 赵;Huan Ting Wang;Paul Webley

    • 刊名:

    • 在线出版时间:

      2009-1-1

  • Highly Efficient Glycerol Acetalization over Supported Heteropoly Acid Catalysts

    • 摘要:

      The acetalization of glycerol with acetone to yield solketal was catalyzed by Cs2.5H0.5PW12O40 (Cs2.5) supported on mesoporous silica under mild conditions. It gave a high glycerol conversion and selectivity to the targeted product even at room temperature (23 °C). We studied the use of both bulk and supported Cs2.5 as catalysts in another highly efficient glycerol acetalization reaction with paraformaldehyde, which gave much higher activity than with formaldehyde solution. For the reaction with acetone, the supported Cs2.5 showed a higher activity than the bulk material because of the high surface area of the mesoporous support. Interestingly, the supported Cs2.5 gave a lower conversion than the bulk for the reaction with paraformaldehyde. This is probably because of the high viscosity of the reaction system with the solid reagent paraformaldehyde. Overall, there is a complex relationship between catalyst, reaction conditions, which include the molar ratio of reactants and temperature, reaction mechanism and thermodynamics that affects the achieved activity and byproduct formation. A discussion about these interactions is included for each reaction.

    • 作者:

      Lin Chen;Bendaoud Nohair;东元 赵;Serge Kaliaguine

    • 刊名:

      ChemCatChem

    • 在线出版时间:

      2018-4-24

  • Organic groups functionalised mesoporous silicates

    • 摘要:

      Great interests have been imparted on organically modified mesoporous silica materials due to their high surface areas, uniform pore sizes and integrated functionality. Besides the inherent character of inorganic and organic components, the interactions between them should also be recognised for the synthesis, including organic-group loading, mesostructure and particle morphology, condensation, as well as organic-group distribution. To obtain long range ordered hybrid materials, several factors, such as relative hydrolysis and condensation rates of the inorganic and organic sources, chemical character such as hydrophobicity/hydrophilicity and acid/base of organic ligand as well as the surfactant category, should be surveyed. A concept of 'combinatorial synthesis' is introduced here for the cases of combining two or more functional units in a typical synthesis into a single one. The silica precursors in the preparation of periodic mesoporous organosilanes (PMOs) are the aggregation of inorganic and organic silicates. The assembly will lead to a unique distribution and high concentration of functional groups. Both the confinement within the mesopores and the pore surface nature will affect the accessibility to the active sites, and therefore, the adsorption and relative applications. These characters win them ample host-guest chemistry. They can seek the opportunities in the fields of catalysis, separation, electronic devices, biomedicines, nanomaterial fabrication, etc.

    • 作者:

      Ying Wan;Dieqing Zhang;Na Hao;东元 赵

    • 刊名:

      International Journal of Nanotechnology

    • 在线出版时间:

      2007

  • Ordered mesoporous materials as adsorbents

    • 摘要:

      Environmental pollution, energy consumption and biotechnology have induced more and more public concerns. Problems imposed by these issues will circulate in the 21st century. Adsorption-based processes may lead to one of the most efficient routes for removal of toxic substances, energy storage and bio-applications. The fundamental and great challenge is developing highly efficient adsorbents. In this regard, ordered mesoporous materials (OMMs) may be the answer in the future. They possess intrinsic high specific surface areas, regular and tunable pore sizes, large pore volumes, as well as stable and interconnected frameworks with active pore surfaces for modification or functionalization. Such features meet the requirements as excellent adsorbents, not only providing huge interface and large space capable of accommodating capacious guest species, but also enabling the possibility of specific binding, enrichment and separation. As a result, these materials have been extensively studied as advanced adsorbents and hundreds of papers have been published since the millennium. In this Highlight, we will mainly summarize and outlook the development in pollution control, gas storage and bioadsorption by using OMMs as adsorbents.

    • 作者:

      Zhangxiong Wu;东元 赵

    • 刊名:

      Chemical Communications

    • 在线出版时间:

      2011-3-8

  • FeN: X and γ-Fe2O3 co-functionalized hollow graphitic carbon nanofibers for efficient oxygen reduction in an alkaline medium

    • 摘要:

      The exploration of efficient, stable, and inexpensive oxygen reduction reaction (ORR) electrocatalysts to replace Pt/C in fuel cells and metal-air batteries still remains an ongoing challenge. Herein, we report an efficient ORR electrocatalyst composed of single-atom FeNx and γ-Fe2O3 nanoparticle co-functionalized hollow graphitic carbon nanofibers (FeNx/Fe2O3-CNFs). It is found that the FeNx species serve as the active sites, while the γ-Fe2O3 nanocrystals function as a co-catalyst to boost the ORR catalytic activity. The obtained FeNx/Fe2O3-CNFs exhibit desirable ORR electrocatalytic activity with a 4-electron transfer pathway, a half-wave potential of 0.81 V approaching that of commercial Pt/C, low hydrogen peroxide yields (<6% at 0.2-0.7 V), long-term stability (87.14% after 30 000 s), and excellent methanol tolerance. The assembled Zn-air battery based on the FeNx/Fe2O3-CNFs has an open circuit voltage of 1.51 V and superior energy density of 920 W h kg-1. This work highlights the significant contribution of the co-catalyst in electrocatalysis.

    • 作者:

      Qiang Yu;Sitian Lian;Jiantao Li;Ruohan Yu;Shibo Xi;Jinsong Wu;东元 赵;立强 麦;Liang Zhou

    • 刊名:

      Journal of Materials Chemistry A

    • 在线出版时间:

      2020-3-28

  • Extension of the stöber method to construct mesoporous SiO2 and TiO2 shells for uniform multifunctional core-shell structures

    • 摘要:

      Core-shell nanoparticles (CSNs) have attracted considerable attention because of their promising applications in a wide range of fields. Recently, substantial efforts have been focused on the development of facile and versatile methods for preparing CSNs with mesoporous SiO2 or TiO2 shells because of their fascinating properties, such as high surface area, large pore channels and high pore volume. This Research News reviews the recent progress in facile, versatile and reproducible approaches which are simply extended from the well-known Stöber method to construct mesoporous SiO 2 and TiO2 shells for uniform multifunctional core-shell nanostructures. Several strategies, including the surfactant-templating process, the long-chain organosilane-assisted approach, the phase transfer assisted surfactant-templating process, and the kinetics-controlled coating approach, are discussed. In addition, new trends in this field for the creation of multifunctional CSNs and novel nanostructures are highlighted.

    • 作者:

      Wei Li;东元 赵

    • 刊名:

      Advanced Materials

    • 在线出版时间:

      2013-1-4

  • Synthesis and characterization of hydroxy-CrAl pillared clays

    • 摘要:

      This paper describes the preparation and characterization of new PILC materials with mixed pillars of Cr3+ and Al3+ intercalated between the layers of montmorillonite. Various Cr/Al ratios were studied to obtain the most suitable physicochemical products. The resulting materials showed basal spacing between 2.49 nm and 1.90 nm for air-dried samples and surface areas between 232 and 283 m2/g. The pillar structure, thermal stability, surface acidity, and reducing behavior of the pillared clay products were determined using 27Al n.m.r., X-ray diffraction (XRD), d.t.a. diffuse reflectance spectroscopy (d.r.s.), e.p.r., i.r., NH3-t.p.d., t.p.r. The results suggest that Cr/Al ratios greatly affect the pillar structure, surface area, acidity, and thermal stability of hydroxy-CrAl pillared clay (CrAl-PILC). The pillar in CrAl-PILC with Cr/Al ratio <1 has a Keggin structure similar to that of hydroxy-Al pillared clay (Al-PILC), but the pillar structures of CrAl-PILC with Cr/Al ratio ≥1 are large polyoxochromium complexes similar to those of hydroxy-Cr pillared clay. The surface acidity and thermal stability are increased by incorporating aluminum into a chromia pillar. There is relatively strong interaction between chromium and alumina in the pillars, which is enhanced with decreasing Cr/Al ratios. Reduction of the chromium(III) was made difficult because of the interaction of chromium with alumina. Catalytic behavior responded to Cr/Al ratio, and incorporating Cr(III) into an alumina pillar increased the kinetic stability and selectivity of the catalyst in the disproportionation of 1,2,4-trimethylbenzene compared with a PILC catalyst containing no chromium.

    • 作者:

      东元 赵;Yashu Yang;Xiexian Guo

    • 刊名:

      Zeolites

    • 在线出版时间:

      1995-1

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