Bio-Inspired Polydopamine: A Versatile and Powerful Platform for Covalent Synthesis of Molecular Sieve Membranes

Inspired by the bioadhesive ability of the marine mussel, a simple, versatile, and powerful synthesis strategy was developed to prepare highly reproducible and permselective molecular sieve membranes by using polydopamine as a novel covalent linker. Attributing to the formation of strong covalent and noncovalent bonds, ZIF-8 nutrients are attracted and bound to the support surface, thus promoting the ZIF-8 nucleation and the growth of uniform, well intergrown, and phase-pure ZIF-8 molecular sieve membranes. The developed ZIF-8 membranes show high hydrogen selectivity and thermal stability. At 150 °C and 1 bar, the mixture separation factors of H₂/CO₂, H₂/N₂, H₂/CH₄, and H₂/C₃H₈ are 8.9, 16.2, 31.5 and 712.6, with H₂ permeances higher than 1.8 × 10^–7 mol·m^–2·s^–1·Pa^–1, which is promising for hydrogen separation and purification

Bicontinuous Zeolitic Imidazolate Framework ZIF-8@GO Membrane with Enhanced Hydrogen Selectivity

Through layer-by-layer (LBL) deposition of a graphene oxide (GO) suspension on a semicontinuous ZIF-8 layer, we have developed a novel bicontinuous ZIF-8@GO membrane. Since only the gaps between the ZIF-8 crystals are sealed by the GO layer due to capillary forces and covalent bonds, the gas molecules can only permeate through the ZIF-8 micropore system (0.34 nm). Therefore, the ZIF-8@GO membranes show high hydrogen selectivity. At 250 °C and 1 bar, the mixture separation factors of H2/CO2, H2/N2, H2/CH4, and H2/C3H8 are 14.9, 90.5, 139.1, and 3816.6, with H2 permeances of about 1.3 × 10–7 mol·m–2·s–1·Pa–1, which is promising for hydrogen separation and purification by molecular sieving

<i>In Situ</i> Synthesis of MOF Membranes on ZnAl-CO₃ LDH Buffer Layer-Modified Substrates

We develop here a urea hydrolysis method to <i>in situ</i> prepare asymmetric ZnAl-CO₃ layered double hydroxide (LDH) buffer layers with various stable equilibrium morphology on porous Al₂O₃ substrates. In particular it is found that well-intergrown ZIF-8 membranes can be directly synthesized on the ZnAl-CO₃ LDH buffer layer-modified substrates, owing to the specific metal–imidazole interaction between ZnAl-CO₃ LDHs and ZIF-8. Other Zn-based MOF membranes, like ZIF-7 and ZIF-90, can also be synthesized with this method. Our finding demonstrates that LDH buffer layer represents a new concept for substrate modification