(217cf) Scaffolded Growth of Thin Zeolite Films Towards High Performance Molecular Separations and Reaction-Separation Technologies

The need for high-resolution control and manipulation of molecules underlies applications, among others, in small molecule separations, integrated reaction-separation technologies, and chemical sensing. Crystalline materials bearing molecular-sized pores (e.g., zeolites, metal organic frameworks (MOFs)) serve as a versatile platform for realizing molecular manipulation through facilitated transport and kinetic and equilibrium molecular selectivity. Despite decades of research in the area of porous inorganic films (i.e., zeolites), the current paradigm for membrane synthesis, that of secondary seeded growth, is plagued by micron (or larger) film thicknesses. The relatively large trans-membrane dimensions lead to stress-induced crack formation and achievable molecular flux that falls short of industrial demands for membrane productivity and desired response time, for example, for chemical sensors. In lieu of attempts to control crystal growth by complex surfactant-based approaches, we employ a hierarchical strategy for templating zeolite film growth in thin (i.e., sub-micron to tens of nanometers), pre-formed mesoporous scaffolds.  Specifically, mesoporous carbon thin films of tunable dimensions serve as scaffolds for zeolite gel infiltration and confined steam-assisted crystallization.Using silicalite-1 as a test bed zeolite, we show that nucleation and growth of high-aspect ratio single crystal domains is achievable within these thin carbon scaffolds, and that the nucleation density and extent of lateral crystal growth/intergrowth can be tuned by controlling synthesis conditions.