Abstract
Metal-organic frameworks (MOFs) have been recognized as a new candidate material for gas separation membranes based on their characteristic pore size and adsorption properties. Recently, pure–MOF membranes have been reported using the in–situ growth method and the secondary growth method, which prepare the pure MOF separation layer. Another preparation method is the counter–diffusion method, which supply the solution of the metal salt and the organic ligand from both sides of the porous support. Among several varieties of MOFs, ZIF–8 is one of the most focused materials for separation membranes, which is effective for propylene/propane separation based on their small difference in molecular size. As an example, we prepared the ZIF–8 membrane using the counter–diffusion method with selective ZIF–8 layer prepared within the porous support. The contribution of diffusive separation for propylene/propane was clarified from the analysis of diffusivity and solubility. In this review, the preparation and the characterization of ZIF–8 membranes for propylene/propane separation are presented.
