New membrane-based molecular separation processes are an essential part of the strategy for sustainable large-scale chemical production. Conventional polymeric membranes generally cannot provide the required level of permeability, selectivity, and robustness. A large literature on ‘hybrid’ or ‘mixed-matrix’ membranes has developed over the last two decades, in which nanoparticles of a higher-performance nanoporous material like a zeolite, metal-organic framework (MOF), or 2D layered structure are dispersed in polymeric membranes to improve their performance while maintaining the good processibility of polymers. However, the performance of such membranes (defined by Robeson-type ‘upper-bound’ curves) is constrained by the polymeric matrix.<br/> <br/>This talk will discuss our new advances in demonstrating the concept of all-nanoporous hybrid membranes (ANHMs). We show that the mixed-matrix membrane concept can be redefined to achieve much higher performance if the membrane matrix and the dispersed phase are both nanoporous crystalline materials. This is challenging since a defect-free polycrystalline nanoporous membrane matrix must be grown while simultaneously incorporating crystals of a second nanoporous material such that there are negligible interfacial defects. As the first example of such a membrane system, we will discussour findings on incorporation of surface-treated nanoparticles of the zeolite MFI during growth of a polycrystalline membrane of the MOF ZIF-8. The resulting all-nanoporous, polymer-free mixed-matrix membrane shows propylene/propane separation characteristics that exceed all known upper-bound performance limits defined for polymers, nanoporous materials, and polymer-based mixed-matrix membranes. We will then show how to generalize this concept to other membrane architectures incorporating assembled nanoparticle arrays as well as stacked/assembled nanosheets. The ANHM concept is an anticipated starting point for fabrication of a new generation of high-performance, structurally complex, membranes containing two or more interconnected nanoporous crystalline phases for wide-ranging uses in chemical separations and related processes.

All-nanoporous hybrid membranes: Redefining upper limits on membrane separation performance

2019 Fall National Meeting

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