Hydrothermal Synthesis of Zeolitic Imidazolate Frameworks-8 (ZIF-8) Crystals with Controllable Size and Morphology

摘要

Zeolitic imidazolate frameworks (ZIFs) is a new class of metal-organicframeworks (MOFs) with zeolite-like properties such as permanent porosity,uniform pore size, and exceptional thermal and chemical stability. Until recently,ZIF materials have been mostly synthesized by solvothermal method. In thisthesis, further analysis to tune the size and morphology of ZIF-8 is done upon ourgroup’s recent success in preparing ZIF-8 crystals in pure aqueous solutions.Compositional parameters (molar ratio of 2-methylimidazole/Zn2+, type of zincsalt reagents, reagent concentrations, addition of surfactants) as well as processparameters (temperature and time) were systematically investigated.Upon characterizations of as-synthesized samples by X-ray powderdiffraction, thermal gravimetric analysis, N2 adsorption, and field-emissionscanning electron microscope, the results show that the particle size andmorphology of ZIF-8 crystals are extremely sensitive to the compotionalparameters of reagent concentration and addition of surfactants. The particle sizeand morphology of hydrothermally synthesized ZIF-8 crystals can be finely tuned;with the size ranging from 90 nm to 4 μm and the shape from truncated cubic torhombic dodecahedron.