Exploring the Framework Hydrophobicity and Flexibility of ZIF-8: From Biofuel Recovery to Hydrocarbon Separations

Ke Zhang, Ryan P. Lively, Chen Zhang, Ronald R. Chance, William J. Koros, David S. Sholl, Sankar Nair

Research output: Contribution to journalArticlepeer-review

217 Scopus citations

Abstract

The framework hydrophobicity and flexibility of ZIF-8 are investigated by a detailed adsorption and diffusion study of a series of probe molecules including ethanol, 1-butanol, water, hexane isomers, xylene isomers, and 1,2,4-trimethylbenzene. The prospects for using ZIF-8 in biofuel recovery and hydrocarbon separations are discussed in terms of adsorption or kinetic selectivities. ZIF-8 shows extremely low water vapor uptakes and is especially suitable for vapor phase butanol-based biofuel recovery. The extraordinary framework flexibility of ZIF-8 is demonstrated by the adsorption of hydrocarbon molecules that are much larger than its nominal pore size, such as m-xylene, o-xylene and 1,2,4-trimethylbenzene. The calculation of corrected diffusion coefficients reveals an interesting spectrum of promising kinetic hydrocarbon separations by ZIF-8. These findings confirm that a molecular sieving effect tends to occur in the sorbate molecular size range of 4-6 Å rather than around the nominal ZIF-8 pore size of 3.4 Å, due to its surprising framework flexibility. © 2013 American Chemical Society.
Original languageEnglish (US)
Pages (from-to)3618-3622
Number of pages5
JournalThe Journal of Physical Chemistry Letters
Volume4
Issue number21
DOIs
StatePublished - Oct 14 2013
Externally publishedYes

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