Zeolite films can be synthesized by various methods, such as in situ, seeded (secondary) growth, vapor phase transport, etc. Most of these methods are based on the hydrothermal synthesis process which involves exposure of the bare or seeded substrates to the synthesis liquid or vapor at elevated temperature. Despite the success of these synthesis methods for many applications, the hydrothermal synthesis process is difficult to scale-up. Therefore, we have been investigating alternative synthesis methods that eliminate hydrothermal synthesis steps.

Here, we report an alternative film fabrication method, so called layer-by-layer deposition. The layer-by-layer deposition method combines deposition of plate-like MCM-22 zeolite crystals on substrates by sonication-assisted covalent attachment1, 2 with evaporation-induced-self-assembly of surfactant-templated silica.3 In this method, although MCM-22 zeolite particles are synthesized by hydrothermal procedure, no hydrothermal synthesis is involved during the film fabrication. The deposition cycles (particle deposition and silica coating) were repeated several times to make compact c-oriented-MCM-22/Silica films on porous á-alumina discs. The composite c-oriented-MCM-22/Silica films exhibited hydrogen ideal selectivities (e.g., H2/N2 ~ 7) above those expected by Knudsen diffusion indicating molecular sieving potential.

(1) Lee, J. S.; Ha, K.; Lee, Y.-J.; Yoon, K. B., Ultrasound-aided remarkably fast assembly of monolayers of zeolite crystals on glass with a very high degree of lateral close packing. Adv. Mater. (Weinheim, Ger.) 2005, 17, (7), 837-841. (2) Yoon, K. B., Organization of Zeolite Microcrystals for Production of Functional Materials. Acc. Chem. Res. 2007, 40, (1), 29-40. (3) Lu, Y.; Ganguli, R.; Drewien, C. A.; Anderson, M. T.; Brinker, C. J.; Gong, W.; Guo, Y.; Soyez, H.; Dunn, B.; Huang, M. H.; Zink, J. I., Continuous formation of supported cubic and hexagonal mesoporous films by sol-gel dip-coating. Nature (London) 1997, 389, (6649), 364-368.