Synthesis of Zeolitic Imidazolate Framework Core鈥揝hell Nanosheets Using Zinc-Imidazole Pseudopolymorphs

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• 作者：Wan-Chi Lee ; Heng-Ta Chien ; Yang Lo ; Hao-Che Chiu ; Tung-ping Wang ; Dun-Yen Kang
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2015
• 出版时间：August 26, 2015
• 年：2015
• 卷：7
• 期：33
• 页码：18353-18361
• 全文大小：565K
• ISSN：1944-8252

文摘

Zeolitic imidazolate frameworks (ZIFs) are an emerging class of microporous materials that possess an organic flexible scaffold and zeolite-like topology. The catalytic and molecular-separation capabilities of these materials have attracted considerable attention; however, crystal-shape engineering in ZIF materials remains in its infancy. This is the first study to report an effective method for tailoring the near-spherical crystal morphology of ZIF-8 using its leaf-like pseudopolymorph, ZIF-L. A thin, uniform layer of ZIF-8 is formed on ZIF-L through heterogeneous surface growth to produce a ZIF-L@ZIF-8 core鈥搒hell nanocomposite. This results in ZIF-8 with a crystal morphology comprising two-dimensional nanoflakes. We characterized the resulting core鈥搒hell crystals using a number of solid-state techniques, including powder X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and nitrogen physisorption. Approximately 16 mass% of ZIF-8 in the core鈥搒hell composites heterogeneous surfacely grown on ZIF-L core crystals. We also investigated the effects of zinc salts, which were used as a source of zinc in the formation of the ZIF-L@ZIF-8 core鈥搒hell nanocomposites. Finally, we assessed the CO₂ adsorption properties of ZIF-8, ZIF-L, and ZIF-L@ZIF-8 core鈥搒hell crystals, the results of which were used to deduce the dynamic and equilibrium adsorption characteristics of various microporous ZIF crystals. The core鈥搒hell materials present hybridized CO₂ uptake and diffusivity of the parent crystals. The proposed method for the synthesis of core鈥搒hell nanocomposites using pseudopolymorphic crystals is applicable to other ZIF systems.