SYNTHESIS AND APPLICATIONS OF MOLECULAR-SIEVE LAYERS AND MEMBRANES

Strategies for the preparation of zeolite molecular sieve membranes an d layers on different substrates are reviewed. Membranes land continuo us thin films) have been synthesized with ZSM-5 (MFI) type molecular s ieves and other zeolites, either as free-standing specimens, grown on various supports according to several schemes, or embedded in polymer matrices. The membranes have been studied for molecule-selective separ ations and for catalytic reactions. Layers of presynthesized molecular sieves have been deposited by means of solgel matrixes and other bond ing agents, molecular attachment layers, and via sputtering or laser a blation techniques. The resulting nanoporous layers have been applied in highly selective sensors, for the alignment of NLO chromophores and for molecular separations. Finally, oriented molecular sieve layers h ave been grown on self-assembled organic mono-and multilayers presenti ng phosphonate groups at the interface. Mixed phosphonate/alkyl films show profound effects on the surface crystallization of metallophospha te molecular sieves, MFI type zeolites have also been grown through th e vapor phase on alkylammonium-modified gold substrates.