Comparison of the hydrothermal stability of ZIF-8 nanocrystals and polycrystalline membranes derived from zinc salt variations

Zeolitic-imidazolate framework-8 (ZIF-8), a representative member of the ZIF class, have attracted extensive application in gas adsorption, membrane separation and catalysis. Since the discovery of ZIF-8, they are always synthesized from zinc nitrate. In this work, we evaluate the hydrothermal stability of ZIF-8 nanocrystals and polycrystalline membranes synthesized from four kinds of common zinc salts. Several physical techniques (X-ray diffraction, scanning electron microscope, and nitrogen adsorption) indicate that ZIF-8 nanocrystals derived from zinc acetate, rather than zinc nitrate, exhibit the highest hydrothermal stability. After immersed in water (∼3 wt%) at 80 °C for 10 days, nanocrystals derived from zinc acetate still could sustain ∼45% relative crystallinity, whereas those from zinc nitrate were transformed to amorphous products. The polycrystalline membrane derived from zinc acetate also exhibits the highest dynamic hydrothermal stability. This work is benefit to the synthesis of ZIF-8 materials for application in water-sensitive systems.