Anomaly in the Chain Length Dependence of n-Alkane Diffusion in ZIF-4 Metal-Organic Frameworks

Hwang S, Gopalan A, Hovestadt M, Piepenbreier F, Chmelik C, Hartmann M, Snurr RQ, Kärger J (2018)

Publication Status: Published

Publication Type: Journal article, Original article

Publication year: 2018

Journal

Molecules MDPI

Publisher: MDPI

Book Volume: 23

Article Number: ARTN 668

Journal Issue: 3

DOI: 10.3390/molecules23030668

Abstract

Molecular diffusion is commonly found to slow down with increasing molecular size. Deviations from this pattern occur in some host materials with pore sizes approaching the diameters of the guest molecules. A variety of theoretical models have been suggested to explain deviations from this pattern, but robust experimental data are scarcely available. Here, we present such data, obtained by monitoring the chain length dependence of the uptake of n-alkanes in the zeolitic imidazolate framework ZIF-4. A monotonic decrease in diffusivity from ethane to n-butane was observed, followed by an increase for n-pentane, and another decrease for n-hexane. This observation was confirmed by uptake measurements with n-butane/n-pentane mixtures, which yield faster uptake of n-pentane. Further evidence is provided by the observation of overshooting effects, i.e., by transient n-pentane concentrations exceeding the (eventually attained) equilibrium value. Accompanying grand canonical Monte Carlo simulations reveal, for the larger n-alkanes, significant differences between the adsorbed and gas phase molecular configurations, indicating strong confinement effects within ZIF-4, which, with increasing chain length, may be expected to give rise to configurational shifts facilitating molecular propagation at particular chain lengths.

Authors with CRIS profile

Maximilian Hovestadt Interdisziplinäres Zentrum Erlangen Catalysis Resource Center (ECRC) Frank Piepenbreier Interdisziplinäres Zentrum Erlangen Catalysis Resource Center (ECRC) Martin Hartmann Professur für Katalyse

Involved external institutions

Universität Leipzig DE Germany (DE) Northwestern University US United States (USA) (US)

How to cite

APA:

Hwang, S., Gopalan, A., Hovestadt, M., Piepenbreier, F., Chmelik, C., Hartmann, M.,... Kärger, J. (2018). Anomaly in the Chain Length Dependence of n-Alkane Diffusion in ZIF-4 Metal-Organic Frameworks. Molecules, 23(3). https://dx.doi.org/10.3390/molecules23030668

MLA:

Hwang, Seungtaik, et al. "Anomaly in the Chain Length Dependence of n-Alkane Diffusion in ZIF-4 Metal-Organic Frameworks." Molecules 23.3 (2018).

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