Hierarchical nanomanufacturing: From shaped zeolite nanoparticles to high-performance separation membranes

Despite more than a decade of intense research on the high-resolution selectivity of thin zeolite films as alternatives to energy-intensive industrial separations, membranes consisting of intergrown, oriented zeolite crystals have fallen short of gaining wide commercial application. Factors including poor performance, high cost, and difficulties in scale up have contributed to this, and have also stunted their application in other niche markets. Until recently, rational design of these materials was limited because of the elusive mechanism of zeolite growth, and forced more empirical approaches. New understanding of zeolite growth along with recent advances in the molecular engineering of crystal microstructure and morphology, assembly of crystal monolayers, and synthesis of ordered films constitute a strong foundation for meeting stringent industrial demands in the future. Together with new processing capabilities, such a foundation should make it possible to synthesize commercially viable zeolite membranes through hierarchical approaches. Such advances open exciting prospects beyond the realm of separations for assembly of novel and complex functional materials including molecular sensors, mechanically stable dielectrics, and novel reaction-diffusion devices. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA.