Synthesis of zeolitic imidazolate framework-67 aerogel by anion exchange

This work reports the synthesis of a zeolitic imidazolate framework-67 (ZIF-67) aerogel by an anion exchange method. A conventional cobalt hydroxide wet gel is prepared as the precursor. Aging of this precursor in 2-methylimidazole/methanol solution at room temperature initiates an anion exchange process in which the OH- anions in the original gel backbone are gradually replaced by the methylimidazole ligand to form the ZIF-67 phase, while the monolithic gel bulk can be retained. After drying the wet gel in supercritical CO2, the resulting aerogel contains the pristine crystalline ZIF-67 as the building blocks and inherits the features of microporosity from ZIF-67 itself and mesoporosity from the aerogel structure, resulting in a hieratical pore structure. With such coexisting micropores and mesopores, the ZIF-67 aerogel has shown faster dye adsorption kinetics compared to its powder counterpart, and the derived Co3O4 material also has better energy storage performance. Replacing the anions in cobalt hydroxide gel by imidazole ligands can give Zeolitic Imidazolate Framework-67 (ZIF-67) gel.The dried ZIF-67 aerogel inherits both the micropores and mesopores features.The hieratical pore structure ensures faster dye adsorption kinetics and better rate capability of the derived Co3O4 electrode.