Experimental study on the structural stability of zeolite imidazolate framework-8 in the alkaline solution

In our previous work, we observed that the structure of zeolite imidazolate framework-8 (ZIF-8) decomposed in the presence of water during the CO2 capture process. However, the structure of ZIF-8 was perfectly retained after adding 5 wt. % or more 2-methylimidazole (HMeim) into the solution. In this work, we investigated the pore structural stability of ZIF-8 when it was suspended in five other alkaline solutions. The results show that the ZIF-8 suspended in monoethanolamine (MEA), methyldiethanolamine (MDEA), and HMeim can still maintain the topological structure whereas the ZIF-8 converted to ZIF-61 and Zn2(Bim)4, respectively, when it came into contact with imidazole (Him) and benzimidazole (HBim). In addition, MEA, MDEA, and HMeim solutions could protect the porous structure of ZIF-8 when ZIF-8 slurry was used for CO2 capture. Nevertheless, the structure of ZIF-8 also collapsed when the concentration of alkaline was lower than 10 wt. %.