ZIF-67 membranes supported on porous ZnO hollow fibers for hydrogen separation from gas mixtures

Co-based zeolitic imidazolate framework-67 (ZIF) membranes present impressive potential to be applied for efficient gas separation. However, the synthesis of ZIF-67 membrane is challenging because ZIF-67 crystals tend to nucleate and grow in the reaction solution rather than on the substrate surface. In this work, ZIF-67 membranes were developed on porous ZnO hollow fibers via in situ solvothermal growth method. The effects of different ZnO supports, surface activation, growth duration, and growing temperatures on the resultant membrane performance were carefully investigated. The optimized ZIF-67 composite hollow fiber membrane displayed desirable permeation performance, ideal selectivities for single gas, and separation factors for gas mixtures. The achieved H2 permeance was 8.98 × 10−8 mol m−2 s−1·Pa−1and ideal selectivities for H2 gas pairs with CO2, N2, and CH4 were 5.14, 11.75, and 15.89, respectively, which compared favorably with other reports in the literature. The developed ZIF-67 membrane exhibited good stability in terms of gas permeances between 30 and 200 °C. Furthermore, the membrane showed almost constant H2 permeance and H2/CH4 separation factor during the 50-h run at 150 °C, demonstrating the excellent thermal stability of membrane. The fabrication of the excellent ZIF-67 membrane can be achieved just in one cycle of growth with high reproducibility.