Sorption Performance and Reproducibility of ZIF-8 Slurry for CO2/CH4 Separation with the Presence of Water in Solvent

In our previous work, a novel slurry approach that suspends zeolitic imidazolate framework-8 (ZIF-8) in solvents (glycol and glycol-2-methylimidazole) for CO2 capture was reported. This approach can efficiently remove CO2 from gas mixtures at normal pressure/temperature. In this work, a system with water coexistence was investigated for real CO2 capture application purposes. Our results show that the structure of the recovered ZIF-8 collapses in the presence of water during the CO2 capture process; however, ZIF-8 can keep its full crystallinity and gas adsorption/separation properties with 5 wt % mIm or more in liquid. Selectivity of CO2/CH4 reaches 76, and its value increases to 190 when 40 wt % mIm was added after four cycling times. Adding suitable mIm can protect the ZIF-8 structure in the environment containing CO2 and water.