(610a) Facile Fabrication of Ultrathin Molecular Sieving ZIF-8 Hollow Fiber Membranes on Polydopamine-Polyethyleneimine Coated Microporous PVDF Supports

Zeolitic Imidazolate Frameworks (ZIFs)-based membrane emerges as a potential and attractive material for molecular sieving gas separation process. ZIF-8 with sodalite topology is one of the most ZIFs studied recently due to its relatively simple fabrication process and environmentally friendly solvent used during its synthesis. However, scaleable formation of thin, defect free films remains challenging. Many ZIF-8 membranes were synthesized by coating ZIF-8 seeds on the surface of inorganic support. However, this process is relatively high cost, complex and the membranes are relatively brittle. Polymeric porous support is one alternative to overcome such problems for inorganic support. The growing of defect free ZIF layers on polymeric support often requires complex surface functionalization as the support frequently lacks in heterogeneous site and ligands needed for the growing process of ZIFs.

To overcome these problems, we chemically-functionalized PVDF hollow fiber porous supports before the deposition of ZIF-8 particles using a simple coating process. Co-deposition of polydopamine (PDA) and polyethyleneimine (PEI) was conducted to induce the crystallization process of ZIF-8 on the support by the presence of cathecol group and produces more uniform coating of PVDF surface compared to traditional PDA deposition. Thin molecular sieving membrane was successfully synthesized simply by 5 hours deposition of support in ZIF-8 precursor solution. Thin layer of ZIF-8 (< 1 μm in thickness) produced very high hydrogen permeance of approximately 105 x 10^-7 mol m^-2 s^-1 Pa^-1, which is one of the highest permeance for ZIF-8 membranes, and H₂/CO₂ selectivity of 7.5. Compared to our previous results utilizing TiO₂/APTES modified PVDF support, the results from this study show slightly lower gas permeances but provides a easier fabrication route.