Synthesis of Ultrathin Zeolitic Imidazolate Framework ZIF-8 Membranes on Polymer Hollow Fibers Using a Polymer Modification Strategy for Propylene/Propane Separation

Polycrystalline zeolitic imidazolate framework ZIF-8 membranes have shown great potential for energy-efficient propylene/propane separation. Their large-scale applications are, however, hampered by the lack of facile and cost-effective processing technologies for ultrathin ZIF-8 membranes on scalable substrates. Here, we report facile preparation of ultrathin ZIF-8 membranes on the bore side of Matrimid hollow fibers based on a polymer modification strategy. Site-selective nature of the method enables a positional control over locations (i.e., bore or shell side) of active ZIF-8 layers on the hollow fibers. The ZIF-8 membranes grown on the bore side of Matrimid hollow fibers with polydimethylsiloxane coating displayed an average propylene permeance and a separation factor of ∼152 × 10 –10 mol·m –2 ·Pa –1 ·s –1 and ∼55, respectively. Optimization of ZIF-8 seeding step resulted in an improvement in propylene permeance (∼369 × 10 –10 mol·m –2 ·Pa –1 ·s –1 ) while maintaining relatively high separation factor (∼40).