Synthesis of Zeolitic Imidazolate Framework Core–Shell Nanosheets Using Zinc-Imidazole Pseudopolymorphs

Abstract

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-shell nanocomposite. This results in ZIF-8 with a crystal morphology comprising two-dimensional nanoflakes. We characterized the resulting core-shell 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-shell 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-shell nanocomposites. Finally, we assessed the CO2 adsorption properties of ZIF-8, ZIF-L, and ZIF-L@ZIF-8 core-shell crystals, the results of which were used to deduce the dynamic and equilibrium adsorption characteristics of various microporous ZIF crystals. The core-shell materials present hybridized CO2 uptake and diffusivity of the parent crystals. The proposed method for the synthesis of core-shell nanocomposites using pseudopolymorphic crystals is applicable to other ZIF systems.

Growth of ZIF-8 on molecularly ordered 2-methylimidazole/single-walled carbon nanotubes to form highly porous, electrically conductive composites

“…In contrast, the solution zinc : 2mIM ratio remains 1 : 8, leading to ZIF-L crystal growth. It has been previously reported that when separately synthesized ZIF-8 and ZIF-L crystals are combined into a single solution, they will coalesce into a new core–shell composite 40. The addition of ox-SWCNTs into low zinc : 2mIM ratio solutions produces similar ZIF-L/ZIF-8/ox-SWCNT composites in a one-pot synthesis.…”

Heterogeneous ZIF-L membranes with improved hydrophilicity and anti-bacterial adhesion for potential application in water treatment

“…MOF-based heterogeneous structures including core-shell structure 44,45 and layer-by-layer structure 41,46 have previously been prepared, and the MOF composites thus-formed show improved separation performance as a result of the engineered pore structure. Specic MOFs can be selected as an interlayer for the growth of target MOFs in terms of the difference in microstructures and chemical characteristics.…”

The Solvent Induced Inter‐Dimensional Phase Transformations of Cobalt Zeolitic‐Imidazolate Frameworks

“…On the other hand, adjusting external synthetic conditions appropriately, such as temperature, guest adsorption or evacuation, and mechanical pressure could also induce structural transformations of ZIFs, forming new thermodynamically or kinetically stable topotactic phases . Although most studies of ZIFs are focused on the specific morphologies/phases and their correlative properties, carefully understanding topotactic phase transformations, with corresponding morphology evolution, is essential for achieving precise morphology‐controlling strategies and further excellent tunable properties …”

“…[13,14] For example, through as olution-mediatedp rocess, ZIFs with differentm orphologies, such as hexagonal nanoparticles, [15] rhombic dodecahedrons, [16] leaf-shaped plates, [17] and cubes [18] were obtained by use of poly(diallyldimethylammonium chloride), cetyltrimethylammonium bromide surfactant, controlo f2 -methylimidazole (2-MIM) concentration, and pH value, respectively.O nt he other hand, adjustinge xternal synthetic conditions appropriately,s uch as temperature, [13] guest adsorption or evacuation, [11,12] and mechanical pressure [19] could also induce structuralt ransformations of ZIFs, forming new thermodynamically or kinetically stable topotactic phases. [20] Although most studies of ZIFs are focused on the specific morphologies/phases andt heir correlativep roperties, [21,22] carefullyu nderstandingt opotactic phase transformations, withc orresponding morphologye volution, is essential for achieving precise morphology-controlling strategies and furtherexcellent tunable properties. [17,18,21,23] IsostructuralZIF-8 and ZIF-67, with sodalite topology,are frequently studied 3D frameworks, and are made up by linking Zn (ZIF-8) or Co (ZIF-67) metal ions with 2-methylimidazole (2-MIM).…”