Synthesis of zeolitic imidazolate framework-8 (ZIF-8) using N,N-dimethylformamide as solvent

Abstract

One of the subclass of metal organic frameworks (MOFs), Zeolitic imidazolate frameworks (ZIFs), like other microporous materials exhibit large surface and pores volume, which make ZIF materials useful in gas storage application. Besides, ZIFs also exhibit high thermal and chemical stability, which are suitable for extreme operational conditions of industrial chemical processes. However, it is still a challenge to tailor the shape and size of ZIFs to match for specific application.

The purpose of this project is to find the optimum conditions when synthesizes ZIF-8 using N,N-Dimethylformamide (DMF) as solvent through varying temperature, concentration of metal salt and organic linker where ZIF-8 crystals have good crystal morphology and narrow size distribution. In this project, the ZIF-8 crystals were synthesized using solvothermal method and zinc nitrate hexahydrate as metal salt while 2-methylimidazole (Hmim) as organic linker. The shape, size and dispersity of ZIF-8 crystals were examined using field-emission secondary electron microscope (FESEM).

Throughout the project, ZIF-8 was found to be very sensitive to change in concentration of metal salt and organic linker when synthesized using 10mL of DMF. A slight change in concentration of metal salt and organic linker would cause large change in crystal morphology and size of ZIF-8 crystals formed. The optimum conditions were found to be at 30mM with concentration ratio of Zn:Hmim = 1:1 and synthesis temperature of 120oC. The crystal morphology of ZIF-8 synthesized using optimum conditions was found to have shape of a cube with truncated edges and thus indicated slower crystal nucleation and growth rates of ZIF-8 when synthesized using DMF as solvent as compared to the other solvents.