Unexpected Molecular Sieving Properties of Zeolitic Imidazolate Framework-8

Chen Zhang, Ryan P. Lively, Ke Zhang, Justin R. Johnson, Oguz Karvan, William J. Koros

Research output: Contribution to journalArticlepeer-review

449 Scopus citations

Abstract

We studied molecular sieving properties of zeolitic imidazolate framework-8 (ZIF-8) by estimating the thermodynamically corrected diffusivities of probe molecules at 35 °C. From helium (2.6 Å) to iso-C 4H 10 (5.0 Å), the corrected diffusivity drops 14 orders of magnitude. Our results further suggest that the effective aperture size of ZIF-8 for molecular sieving is in the range of 4.0 to 4.2 Å, which is significantly larger than the XRD-derived value (3.4 Å) and between the well-known aperture size of zeolite 4A (3.8 Å) and 5A (4.3 Å). Interestingly, because of aperture flexibility, the studied C 4 hydrocarbon molecules that are larger than this effective aperture size still adsorb in the micropores of ZIF-8 with kinetic selectivities for iso-C 4H 8/iso-C 4H 10 of 180 and n-C 4H 10/iso-C 4H 10 of 2.5 × 10 6. These unexpected molecular sieving properties open up new opportunities for ZIF materials for separations that cannot be economically achieved by traditional microporous adsorbents such as synthetic zeolites. © 2012 American Chemical Society.
Original languageEnglish (US)
Pages (from-to)2130-2134
Number of pages5
JournalThe Journal of Physical Chemistry Letters
Volume3
Issue number16
DOIs
StatePublished - Jul 30 2012
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUS-I1-011-21
Acknowledgements: We would like to thank Dr. Ronald Chance for insightful comments on the manuscript and Hongzhi Wang for help on crystal size analysis. This publication is based on work supported by 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.

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