While polymers are frequently used as membranes in industrial-scale separations due to their ease of synthesis and processing, their performance is limited by a well-documented permeability/selectivity tradeoff. A class of metal-organic frameworks known as zeolitic imidazolate frameworks (ZIFs) has also demonstrated great promise as selectively permeable membranes. These permanently porous crystals limit the diffusion of species too large to fit through the apertures into their pores, making them effective molecular sieves that do not suffer the tradeoffs inherent to polymeric membranes. However, ZIF films are generally difficult to process at scale, and polymer-ZIF composites are therefore an attractive target. Here, we demonstrate a method to chemically convert zinc oxide nanocrystal films into ZIF coatings on a microporous polymer surface, providing a scalable alternative to traditional ZIF film syntheses. Our layered composites are less than 1 μm thick, and the morphology and composition of the ZIF coating can be controlled by changing the solvent mixture in which the chemical conversion occurs. Interesting multi-layer structures, including ZIF/ZIF bilayers on polymer, are demonstrated. The transformation of these films is studied using scanning electron microscopy and X-ray absorption spectroscopy, and the findings offer insight into both the growth trajectory of these ZIF films and interactions at the polymer-ZIF interface.

Layered polymer-zeolitic imidazolate framework composites fabricated using sacrificial, metal-oxide, nanocrystal precursors

251st National Meeting (2016)

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