High performance ZIF-8 molecular sieve membrane on hollow ceramic fiber via crystallizing-rubbing seed deposition

► Hollow fiber alumina tube was used as membrane support. ► A novel crystallizing-rubbing seeding method was developed. ► High quality ZIF-8 membrane was obtained by secondary growth. ► High permeance of hydrogen was achieved. ► Excellent H2 separation performance was reached. In this report, a continuous well-intergrown ZIF-8 membrane on hollow ceramic fiber tube was successfully synthesized by a novel crystallizing-rubbing seed deposition. It is shown that the obtained ZIF-8 membrane was compact and defect-free, with a thickness of about 5μm. The obtained membrane displayed high H2 molecular sieve separation performance. Specifically, the H2 permeance reached an excellent value of 1.1×10−6molm−2s−1Pa−1, and the ideal separation factors for H2/CO2, H2/N2 and H2/CH4 were calculated to be 5.2, 7.3 and 6.8 at room temperature, respectively. We show that the fine seeds generated by crystallizing-rubbing play the key role for enhancing the heterogeneous nucleation of ZIF-8 crystals, which thus result in a high quality ZIF-8 membrane.