ZIF-8 membranes supported on silicalite-seeded substrates for propylene/propane separation

Zeolitic Imidazolate Framework-8 (ZIF-8) membranes have shown great potential for effective separation of industrially important propylene/propane gas mixtures. In this work, we coated the silicalite seed nanoparticles on the anodic alumina oxide (AAO) substrate in order to increase membrane-substrate bonding. ZIF-8 membrane was synthesized on a silicalite-seeded AAO substrate by secondary growth method. It was found that high quality ZIF-8 membrane was fabricated due to strong attachment of silicalite seed crystals to AAO substrates through hydrogen bonding. Moreover, when ZnCl2 was used as the Zn source, the ZIF-8 layer was formed with larger ZIF-8 crystal size and a more intergrown surface than the layer in which ZnNO3 was used. An excellent propylene/propane separation factor of 170 was obtained in a silicalite-seeded ZIF-8 membrane with ZnCl2, which is twice that of a ZIF-8 membrane synthesized without the seeding process, and which is 3.6 times higher than a silicalite-seeded ZIF-8 membrane with ZnNO3.