The polydimethylsiloxane (PDMS) coating penetrated into the underneath ZIF-8 polycrystalline membrane not only blocking the inter-crystalline defects but also hindering the flexibility of the ZIF-8 framework, resulting in an unusual and highly desired increase in the separation selectivity of the CH/CH mixture under high feeding pressures.

Morphology-tailoring of metal–organic frameworks (MOFs) is essential for their specific application in molecular-separation, catalysis, and drug-delivery. However, precision syntheses of uniform MOFs crystals with anisotropic shape are still challenging. Herein, a morphological map for monodisperse ZIF-8 crystals with five distinctive shapes was constructed in terms of the synthetic conditions. It was revealed that the formation mechanism for ZIF-8 crystals with various shapes is strongly dependent on the concentration of cetyltrimethylammonium bromide (CTAB) added, not limited to the traditional capping mechanism for MOFs and metal nanocrystals. The generality of this strategy was also verified through the successful morphology-controllable synthesis of ZIF-67 crystals. The effect of ZIF-8 morphology on separation performance of resulting cross-linked poly­(ethylene oxide) (XLPEO)-based mixed-matrix membranes for C3H6/C3H8 mixtures was also evaluated.

Continuous ZIF-67 polycrystalline membranes with effective propylene/propane separation performances were successfully fabricated through the incorporation of zinc ions into the ZIF-67 framework. The separation factor increases from 1.4 for the pure ZIF-67 membrane to 50.5 for the 90% zinc-substituted ZIF-67 membrane.

Zeolitic imidazolate framework-8 (ZIF-8) membrane has shown great potential for propylene/propane separation based on molecular sieving mechanism. Although diverse synthesis strategies were applied to prepare ZIF-8 membranes, it is still a challenge for reproducible fabrication of high-quality membranes. In this study, high-quality ZIF-8 membranes were prepared through hydrothermal synthesis under the partial self-conversion of sputter-coated ZnO layer on porous α-alumina supports.The reproducibility was significantly improved, compared with that from sol-gel coated ZnO layer, due to the highly controllable sputtering deposition of ZnO precursor. The relationship between the quality of as-synthesized membrane and amount of deposited ZnO was also determined. The effect of pressure drop in C 3 H 6 /C 3 H 8 separation on separating performance was also examined.

Zeolitic imidazolate framework ZIF-8 has shown great potential for effective separation of hydrocarbon mixtures based on its intrinsic ultramicroporous feature. In order to explore the permeation and diffusion properties of hydrocarbons through ZIF-8 membrane, high-quality ZIF-8 membranes with a separation factor of ~90 for propylene/propane are successfully prepared via optimizing the activation processes. Single-component permeation data for hydrocarbons (C1~C4) through the improved ZIF-8 membrane are measured and analyzed by Maxwell-Stefan (MS) model to get the transport diffusivities of these hydrocarbons. The diffusivity values of 2 hydrocarbon compare well with those obtained by other experimental techniques. Binary mixture permeation also can be well predicted through single-component adsorption parameters.