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Issue 35, 2012
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Flexibility and swing effect on the adsorption of energy-related gases on ZIF-8: combined experimental and simulation study

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Abstract

ZIF-8, a prototypical zeolitic porous coordination polymer, prepared via the self-assembly of tetrahedral atoms (e.g. Zn and Co) and organic imidazolate linkers, presents large cavities which are interconnected by narrow windows that allow, in principle, molecular sieving. However, ZIF-8 shows flexibility due to the swing of the imidazolate linkers, which results in the adsorption of molecules which are too large to fit through the narrow window. In this work, we assess the impact of this flexibility, previously only observed for nitrogen, and the level of agreement between the experimental and simulated isotherms of different energy-related gases on ZIF-8 (CO2, CH4 and alkanes). We combine experimental gas adsorption with GCMC simulations, using generic and adjusted force fields and DFT calculations with the Grimme dispersion correction. By solely adapting the UFF force field to reduce the Lennard-Jones parameter ε, we achieve excellent agreement between the simulated and experimental results not only for ZIF-8 but also for ZIF-20, where the transferability of the adapted force field is successfully tested. Regarding ZIF-8, we show that two different structural configurations are needed to properly describe the adsorption performance of this material, demonstrating that ZIF-8 is undergoing a structural change during gas adsorption. DFT calculations with the Grimme dispersion correction are consistent with the GCMC and experimental observations, illustrating the thermodynamics of the CH4 adsorption sites and confirming the existence of a new adsorption site with a high binding energy within the 4-ring window of ZIF-8.

Graphical abstract: Flexibility and swing effect on the adsorption of energy-related gases on ZIF-8: combined experimental and simulation study

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Publication details

The article was received on 09 Apr 2012, accepted on 23 Jun 2012 and first published on 27 Jun 2012


Article type: Paper
DOI: 10.1039/C2DT30774J
Citation: Dalton Trans., 2012,41, 10752-10762
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    Flexibility and swing effect on the adsorption of energy-related gases on ZIF-8: combined experimental and simulation study

    D. Fairen-Jimenez, R. Galvelis, A. Torrisi, A. D. Gellan, M. T. Wharmby, P. A. Wright, C. Mellot-Draznieks and T. Düren, Dalton Trans., 2012, 41, 10752
    DOI: 10.1039/C2DT30774J

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