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 language||English (US)|
|Number of pages||5|
|Journal||The Journal of Physical Chemistry Letters|
|State||Published - Oct 14 2013|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUS-I1-011-21
Acknowledgements: This material is based upon work supported partially by the following agencies: Department of Energy under Award Number DE-FOA-0000096, and Algenol Biofuels. W.J.K. also acknowledges Award No. KUS-I1-011-21 made by King Abdullah University of Science and Technology (KAUST).
This publication acknowledges KAUST support, but has no KAUST affiliated authors.