Anomaly in the Chain Length Dependence of n-Alkane Diffusion in ZIF-4 Metal-Organic Frameworks
| Autor: | Martin Hartmann, Jörg Kärger, Frank Piepenbreier, Christian Chmelik, Arun Gopalan, Seungtaik Hwang, Maximilian Hovestadt, Randall Q. Snurr |
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| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
Materials science
Technische Fakultät Pharmaceutical Science 02 engineering and technology 010402 general chemistry Thermal diffusivity 01 natural sciences Article Analytical Chemistry lcsh:QD241-441 Adsorption lcsh:Organic chemistry Drug Discovery Alkanes Molecule GCMC simulation Physical and Theoretical Chemistry Diffusion (business) Metal-Organic Frameworks Alkane chemistry.chemical_classification Molecular diffusion Molecular Structure Organic Chemistry 021001 nanoscience & nanotechnology 0104 chemical sciences ZIF-4 chemistry n-alkanes transport diffusivity commensurate/incommensurate adsorption Chemistry (miscellaneous) Chemical physics Yield (chemistry) ddc:540 Zeolites Molecular Medicine 0210 nano-technology Monte Carlo Method Zeolitic imidazolate framework |
| Zdroj: | Molecules : A Journal of Synthetic Chemistry and Natural Product Chemistry Molecules; Volume 23; Issue 3; Pages: 668 Molecules, Vol 23, Iss 3, p 668 (2018) |
| ISSN: | 1420-3049 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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