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  • 1.
    Kapaca, Elina
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Burton, Allen
    Terefenko, Eugene
    Vroman, Hilda
    Weston, Simon C.
    Kochersperger, Meghan
    Afeworki, Mobae
    Paur, Charanjit
    Koziol, Lucas
    Rayikoyitch, Peter
    Xu, Hongyi
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Willhammar, Tom
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Small Pore Aluminosilicate EMM-37: Synthesis and Structure Determination Using Continuous Rotation Electron Diffraction2019In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 58, no 19, p. 12854-12858Article in journal (Refereed)
    Abstract [en]

    A new aluminosilicate zeolite, denoted EMM-37, with a 3D small pore channel system, has been synthesized using a diquaternary ammonium molecule as the structure directing agent (SDA) and metakaolin as the aluminum source. The structures of both as-made and calcined forms of EMM-37 were solved and refined using continuous rotation electron diffraction (cRED) data. cRED is a powerful method for the collection of 3D electron diffraction data from submicron- and nanosized crystals, which allows for successful solution and refinement of complex structures in symmetry as low as P (1) over bar.

  • 2.
    Kapaca, Elina
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Willhammar, Tom
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Detailed Structural Survey of the Zeolite ITQ-39 by Electron Crystallography2017In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 17, no 4, p. 1910-1917Article in journal (Refereed)
    Abstract [en]

    The structure of the highly faulted zeolite ITQ-39 was previously determined by electron crystallography, revealing the presence of stacking disorders and twinning. Structural models of three polytypes were proposed, providing a basic description of the ITQ-39 material. Here, a more comprehensive description of the complex structure of the ITQ-39 zeolite is presented based on a onedimensional periodic building unit. The study includes a detailed description of the structural defects in the material based on the analysis of high resolution transmission electron microscopy images and information on how the defects influence the pore system. A new structure arrangement with alternating twinning was found in the material, and structural models of three twinned end-members are presented. The geometry of the different structural models is evaluated to understand the formation of the crystals.

  • 3.
    Su, Jie
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kapaca, Elina
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Liu, Leifeng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Georgieva, Veselina
    Wan, Wei
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Valtchev, Valentin
    Hovmöller, Sven
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Structure analysis of zeolites by rotation electron diffraction (RED)2014In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 189, p. 115-125Article in journal (Refereed)
    Abstract [en]

    Single crystal X-ray diffraction and powder X-ray diffraction (PXRD) are powerful methods for determination of unknown crystal structures including zeolites. However, these techniques have some limitations. For instance, single crystal X-ray diffraction requires large enough crystals which are often difficult to synthesize. For powder X-ray diffraction, peak indexing and intensity extraction become difficult if there exist peak broadening caused by small crystal sizes and peak overlap due to large unit cell and high symmetry. This becomes even more complicated for samples that contain more than one phase. We developed a new rotation electron diffraction (RED) method that can overcome these limitations. Almost complete three-dimensional electron diffraction datasets can be collected from micron- or nano-sized single crystals in a transmission electron microscope by combining electron beam tilt and goniometer tilt. Here, we demonstrate the power and limitations of the RED method for ab initio structure determination of four sub-micron sized zeolites, including a calcined silicalite-1, an EUO-type germanosilicate, an FER-type aluminogermanosilicate and an AST-type aluminogermanosilicate. The latter three zeolites were found in multiphasic samples. We show how the tilt range, tilt step and resolution affect the unit cell determination, structure solution and structure refinement. The EUO-, FER- and AST-type zeolites were found in two multiphasic samples in the Al-Ge-Si system, which were also characterized by PXRD and N-2 sorption.

  • 4. Zhang, Chuanqi
    et al.
    Kapaca, Elina
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Li, Jiyang
    Liu, Yunling
    Yi, Xianfeng
    Zheng, Anmin
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Jiang, Jiuxing
    Yu, Jihong
    An Extra-Large-Pore Zeolite with 24 x 8 x 8-Ring Channels Using a Structure-Directing Agent Derived from Traditional Chinese Medicine2018In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 57, no 22, p. 6486-6490Article in journal (Refereed)
    Abstract [en]

    Extra-large-pore zeolites have attracted much interest because of their important applications for processing larger molecules. Although great progress has been made in academic science and industry, it is challenging to synthesize these materials. A new extra-large-pore zeolite SYSU-3 (Sun Yat-sen University no?) has been synthesized by using a novel sophoridine derivative as an organic structure-directing agent (OSDA). The framework structure was solved and refined using continuous rotation electron diffraction (cRED) data from nanosized crystals. SYSU-3 exhibits a new zeolite framework topology, which has the first 24 x 8 x 8-ring extra-large pore system and a framework density (FD) as low as 11.4 T/1000 angstrom(3). The unique skeleton of the OSDA plays an essential role in the formation of the distinctive zeolite structure. This work provides a new perspective for developing new zeolilic materials by using alkaloids as cost-effective OSDAs.

1 - 4 of 4
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