However, several studies reported the instability of ZIFs materials. A study stated that ZIF-8 crystallites were unstable in water under ambient conditions . ZIF-8 crystals were dissolved in water, forming zinc and imidazolate ions . They undergo a phase shift to a dense structure and a leaf-like morphology . However, it is essential to mention that the conversion depends on the ratio of ZIF-8/water . The degradation of ZIF-8 is higher in culture media than in deionized water . This observation could be due to the reaction between the released zinc ions with phosphate ions in phosphate-buffered saline (PBS) or with organic moieties in Luria Bertani (L.B.) media. The degradation of ZIF-8 in L.B. and PBS media was 70-80 wt.%, which is higher than in pure water (22 wt.%) . The stability of ZIFs materials can be enhanced by shielding the metalligand bond from the attack of water molecules . separation of gas, as well as for size-selective catalysis due to their pore size (< 5 Å) . A study using thermodynamically corrected diffusivities of probe molecules at 35 °C showed that the adequate aperture size of ZIFs materials such as ZIF-8 was 4.0-4.2 Å . These values are significantly larger than pore apertures estimated using X-ray diffraction (XRD), showing an aperture size of 3.4 Å . This observation indicates that ZIF-8 showed an aperture size similar to well-known porous materials such as zeolite 4A (3.8 Å) and 5A (4.3 Å). The structures of most of the reported ZIFs are flexible. The aperture diameter of ZIF-8 increases from 3.4 to 4.0 Å after gas adsorption .