A simple seed-embedded method to prepare ZIF-8 membranes supported on flexible PESf hollow fibers

With intrinsic porous structure, unique chemical versatility and abundant application opportunities, MOF membranes have attracted substantial research enthusiasm. Most of these supported MOF membranes are prepared on the rigid ceramic substrates. If the MOF membrane possesses flexibility, the application opportunities will be expanded. This paper presents the synthesis of ZIF-8 membranes on the flexible polyethersulfone (PESf) hollow fibers by using a facile seed-embedded method. The resultant membranes were characterized by scanning electron microscopy, energy dispersive X-ray, X-ray diffraction and fourier transform infrared spectroscopy. The prepared membranes were in a continuous and compact structure and showed good molecular sieve performance of H₂ over CO₂, N₂ and CH₄ with H₂ permeance up to 1.1 × 10⁻⁵ mol·m⁻² s⁻¹ Pa⁻¹. Due to the preferential adsorption, ZIF-8/PESf composite membrane exhibited high permeance of H₂, N₂, and CH₄ compared to CO₂, showing potential applications in efficient CO₂ capture from industrial mixtures. The association between the gas permeation, the amount of embedded ZIF-8 crystals and the membrane thickness was also clarified. The reproducibility was significantly improved compared to the conventional secondary seeding method. Attributed to the strong adhesion between the ZIF-8 and the PESf, the membranes displayed excellent stability and flexibility which could sustain bending up to 90° without breaking the ZIF-8 membrane. This seed-embedded method is not only simple, but also has good reproducibility and scalability.