In this study, the synthesis of zeolitic imidazole framework (ZIF-8) in water was systematically studied using 6 zinc sources (Zn(OAc) 2 , ZnSO 4 , Zn(NO 3 ) 2 , ZnCl 2 , ZnBr 2 , ZnI 2 ), respectively, under different conditions at room temperature without using any additives. It was found that Zn(OAc) 2 is the best precursor and the resultant ZIF-8 particles have the best quality with rhombic dodecahedron morphology. The concentration of 2-methylimidazole (Hmim), molar ratio Hmim/Zn and water content all have significant impacts on the morphology, particle size, and crystallinity of ZIF-8. Further result analysis reveals that 3 key reactions are involved in the ZIF-8 formation which needs five steps in ZIF-8 structural evolution.This study provides a deep understanding of the crystallization process of ZIF-8 particles in a waterbased system.

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