Highly Oriented Thin Membrane Fabrication with Hierarchically Porous Zeolite Seed

Nanosized zeolite is widely used as seed for high quality zeolite membranes fabrication, while its complicated synthesis routine limits large-scale productions. In this work, a non-nanosized cubic hierarchically porous TS-1 zeolite (HTS-1), obtained by basic hydrothermal treatment of conventional ellipsoid solid TS-1, is used as seed to prepare highly oriented thin membranes. A capillary condensation phenomenon resulting from the unique hierarchically porous structure benefits gel attachment. Moreover, abundant ledges, kinks, and terraces on the HTS-1 surface promote epitaxial growth of the membrane. In contrast, the solid TS-1 seed induces intergrowth dominantly, which results in a thick TS-1 membrane. The HTS-1 membrane demonstrates superior CO2/N2 separation properties compared to the TS-1 one. It associates with thin oriented membrane morphology, leading to exposure of a high Miller index surface and less diffuse distance and tortuosity. The results suggest beneficial effects of a hierarchically porous TS-1 zeolite seed on the interfacial crystal growth for membrane fabrication. A similar conclusion is applicable to the case of a hierarchically porous zeolite β. This work develops a facile approach to obtain a highly oriented thin zeolite membrane with enhanced separation properties.