Controlled Growth of Millimeter Scale ZIF-8 Single Crystal in Organic Solvents: Reversible Structural Conformation Investigated by Single-Crystal XRD at Various Temperatures

Among several zeolitic imidazolate frameworks (ZIFs), ZIF-8, in which 2-methylimidazole and Zn ions are regularly arranged, has attracted great attention due to its special crystal and pore structure. ZIF-8 crystals of various sizes and shapes have been reported depending on synthesis parameters such as the molar ratio of organic ligands and metal ions, solvent, and temperature, but large-scale single-crystal ZIF-8 has been clearly reported photographically. Herein, millimeter-sized single crystal ZIF-8 has been synthesized via the solvothermal method in N,N-diethylformamide. The 1-mm single crystal is examined by N2 adsorption isotherms, scanning electron microscope, etc. Single crystal X-ray diffraction is also used to carefully study the framework mobility at various temperatures.