Zeolitic Imidazolate Framework Membranes with a High H2 Permeance Fabricated on a Macroporous Support with Novel Spherical Porous Hybrid Materials

An original synthesis strategy for tubular zeolitic imidazolate framework (ZIF) membranes was developed by the deposition of a novel porous amorphous hybrid material prepared by 3-isocyanatopropyltrimethoxysilane (IPTMS) and ZIF-8 crystals onto a coarse macroporous α-Al2O3 tubular support. This porous amorphous hybrid material (ZIF-8-IPTMS) not only strongly adhered to the support but also repaired the defects to make the support surface smooth due to the abundant hydroxyl groups and the appropriate particle size. Using this synthesis strategy, we successfully prepared a high-quality ZIF-8 membrane on an inorganic α-Al2O3 tubular support via the sufficient heterogeneous nucleation sites provided by the amino groups of ZIF-8-IPTMS. This ZIF-8 membrane with an ultrathin thickness of approximately 0.9 μm was prepared, and its ideal H2/CO2 selectivity increased as the temperature increased. The membrane exhibited a competitive selectivity of 13.8 with a remarkably high H2 permeance of 1.46 × 10–5 mol·m–2·s–1·Pa–1 at 90 °C and 0.1 MPa. H2/CO2 binary gas permeation measurements indicated a separation factor of 9.2, and the H2 permeance was maintained at 0.83 × 10–5 mol·m–2·s–1·Pa–1 at 90 °C and 0.1 MPa. This synthesis strategy was also suitable to fabricate ZIF-67 membranes. The ZIF-67 membrane with a thickness of approximately 1.2 μm exhibited a H2/CO2 ideal selectivity of 5.3 and maintained a high H2 permeance of 1.06 × 10–5 mol·m–2·s–1·Pa–1 at 35 °C and 0.1 MPa.