Differences in Phase Change Processes Upon Heating Between Co and Zn-ZIF-4 Compounds

Zn and Co-ZIF-4 meta-stable compounds adopt the same topology of Zeolitic imidazolate frameworks (ZIF)-4, but differ in the metal nodes (Zn versus Co). Using calorimetric and thermogravimetric analysis, here we characterized their differences in phase change processes. Upon heating, the framework of Co-ZIF-4 meta-stable crystal undergoes the crystal-to-amorphous phase transition at 590[Formula: see text]K, which is somewhat lower than the corresponding transition previously reported in the corresponding Zn-ZIF-4. In addition, the recrystallization rate for amorphous Co-ZIF-4 is relatively higher than the corresponding one of Zn-ZIF-4. Finally, the forming Co–zni crystal begins to melt at about 824[Formula: see text]K, accompanied by quick decomposition, whereas Zn–zni undergoes complete melting which finishes at around 850[Formula: see text]K without any decomposition. Based on their differences in chemistry for Co and Zn, we elucidated the chemical origin of the discrepancies of phase transition process for Zn and Co-ZIF-4 compounds upon heating.