Facile synthesis of molecular sieve membranes following “like grows like” principle

Because of poor heterogeneous nucleation of MOF on the ceramic support surface, it is usually difficult to prepare defect-free metal-organic framework (MOF) layers as shape-selective membrane on the native ceramic supports by a direct solvothermal synthesis route. In the present work, inspired by “like dissolves like” principle, a simple and facile synthesis strategy was developed to prepare highly reproducible and permselective zeolitic imidazolate framework ZIF-8 membranes on the 1H,1H,2H,2H-perfluoroalkyltriethoxysilanes (POTS) modified α-Al₂O₃ disks. Attributing to the enhancement of surface hydrophobicity of the α-Al₂O₃ supports after POTS modification, hydrophobic ZIF-8 membranes are tending to grow well on the hydrophobic surface following the “like grows like” principle. Thus a well-intergrown ZIF-8 membrane with a thickness of about 20 µm has formed on the POTS-modified α-Al₂O₃ disks. The developed ZIF-8 membranes show high hydrogen selectivity and thermal stability. At 200 °C and 1 bar, the mixture separation factors of H₂/CO₂, H₂/N₂, H₂/CH₄, and H₂/C₃H₈ are 15.8, 22.6, 40.6, and 549.3, with H₂ permeances higher than 2.1 × 10⁻⁷ mol·m⁻²·s⁻¹·Pa⁻¹, which is promising for hydrogen separation and purification.