Gel-Modulated Growth of High-Quality Zeolite Membranes.

Trade-off between thickness (and thus gas permeance) and quality (and thus selectivity) of zeolite membranes significantly restricts their wide application. It is challenging to maintain the membrane thickness while minimizing nonselective defects in the selective membrane layer. Currently, continuous change of the synthesis gel concentration during membrane synthesis, instead of high gel concentration for membrane "skeleton" growth and low gel concentration for slow crystal growth to merge "skeleton" crystals, usually leads to thick membranes to compensate for the low selectivity. In this work, we report a gel-modulated synthesis approach to engineer the zeolite membrane synthesis. The gel concentration was suddenly reduced by a quenching process in the middle of the membrane synthesis, leading to reduced nuclei formation and crystal growth rate in the following synthesis process. Membrane quality was significantly improved without increasing membrane thickness, leading to a great increase in membrane selectivity but without sacrifice of gas permeance. Moreover, as an example, highly reproducible SAPO-34 membranes were successfully prepared by the gel-modulated growth method. We expect this novel synthesis strategy might be a viable and economic way of growing thin and high-quality zeolite membranes.