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Zeolitic imidazolate framework membranes made by ligand-induced permselectivation

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Science  07 Sep 2018:
Vol. 361, Issue 6406, pp. 1008-1011
DOI: 10.1126/science.aat4123

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The makings of permeable membranes

A challenge in making membranes is finding ways to control the pore structure during the fabrication process or through postfabrication treatment. The deposition of a zeolitic imidazolate framework material called ZIF-8 onto an alumina support gives a dense, impermeable material. However, when Ma et al. exposed this material to vapors of 2-methylimidazole, it transformed into a porous material able to separate propylene from propane.

Science, this issue p. 1008

Abstract

Zeolitic imidazolate framework (ZIF) membranes are emerging as a promising energy-efficient separation technology. However, their reliable and scalable manufacturing remains a challenge. We demonstrate the fabrication of ZIF nanocomposite membranes by means of an all-vapor-phase processing method based on atomic layer deposition (ALD) of ZnO in a porous support followed by ligand-vapor treatment. After ALD, the obtained nanocomposite exhibits low flux and is not selective, whereas after ligand-vapor (2-methylimidazole) treatment, it is partially transformed to ZIF and shows stable performance with high mixture separation factor for propylene over propane (an energy-intensive high-volume separation) and high propylene flux. Membrane synthesis through ligand-induced permselectivation of a nonselective and impermeable deposit is shown to be simple and highly reproducible and holds promise for scalability.

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