Zeolitic Imidazolate Framework Membranes on Silicate-Seeded Substrates for Propylene/Propane Separation

In this work, we have successfully developed the highly propylene-selective of Zeolitic-Imidazolate Framework (ZIF-8) membrane on a silicate-seeded porous Anodic Alumina Oxide (AAO) support. These membranes were prepared at ambient conditions via a novel seeding technique followed by secondary growth. The methods showed an effective way to produce high-quality ZIF-8 membranes by achieving strong attachment of silicalite nanocrystals to AAO supports. To control the membrane microstructures, we investigated the important synthesis variables such as seeding materials, synthesis time, and nature of the metal source. It was found that zinc chloride as a metal source with a synthesis time of 10 hours and well-intergrown layers with 1 μm thickness, ZIF-8 membranes were synthesized. The resulting ZIF-8 membranes present a great propylene/propane separation factor of ∼197 with propylene permeance of 0.62 × 10^-8 mol m^-2 s^-1 Pa^-1. The membranes were analyzed using SEM-EDX, XPS, XRD, BET and FTIR techniques to investigate the impact of seeding, synthesis time, and Zn source on the ZIF-8 membrane structure and separation performance.