Solvothermal synthesis of porous hydrangea-like zeolitic imidazole framework-8 (ZIF-8) crystals

Zeolitic imidazole framework-8 (ZIF-8) with a novel porous hydrangea-like morphology was successfully synthesized with solvothermal synthesis using zinc nitrate as the metal source and 2-methylimidazole as the organic ligand. The effects of reaction temperature and reaction time on the morphology of the crystal were investigated and the samples were characterized in detail. The results show that the porous hydrangea-like ZIF-8 crystal can be obtained at different temperatures from 110 to 140 °C. At the same temperature, with the increase of reaction time, the particles are transformed from porous hydrangea-like into the rhombohedral polyhedron. Combining primary particle self-assembly with Ostwald ripening, we propose a mechanism for the formation of porous hydrangea-like ZIF-8 in a classical crystal growth pathway. In comparison, ZIF-8 with rhombohedral polyhedron can be quickly synthesized via microwave-assisted synthesis.