Molecular Sieve Zeolitic-Imidazolate Framework ZIF-90 Thin Films and Membranes for Gas Separation Applications

Hydrocarbon separation in the industry is challenging and currently achieved by well-established relative energy intensive and multi-column distillation processes. Even if many promising membrane-based separation technologies were developed to deal with the issues in hydrocarbon separations, we could find limited practical applications by polymeric membranes because of low selectivity and stability in separation process of industry. Zeolitic-imidazolate frameworks (ZIFs) have large potential owing to their well-defined aperture size, robustness, and excellent thermal/chemical stability. Recently, ZIF-90 membranes with effective aperture size ~ 5.0 Å have been investigated to have a large potential to separate C4 hydrocarbons such as n-butane/i-butane mixture which cannot be effectively separated by ZIF-8 membranes. However, there are limited numbers of reports about ZIF-90 membrane fabrication and C4 hydrocarbon separation performance of ZIF-90 membranes. Herein, we proposed a new method to fabricate thin ZIF-90 membranes (thickness ~ 3 – 5 µm) for C4 hydrocarbon separation via Microwave (MW) assisted seeding of ZIF-8 on alumina supports, solvent-assisted linker exchange, and tertiary growth. Even though the cracks formed after drying, saturated drying technique was applied to reduce the formation of cracks efficiently. In addition, several binary gas permeation measurements have been conducted to obtain the performance of the as-synthesized ZIF-90 membranes. The gas permeation measurement for our targeted C4 hydrocarbons is still waiting until the equipment and C4 hydrocarbon were ready for permeation measurement