A Combined Experimental鈥揅omputational Investigation of Methane Adsorption and Selectivity in a Series of Isoreticular Zeolitic Imidazolate Frameworks

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• 作者：Yao Houndonougbo ; Christopher Signer ; Ning He ; William Morris ; Hiroyasu Furukawa ; Keith G. Ray ; David L. Olmsted ; Mark Asta ; Brian B. Laird ; Omar M. Yaghi
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：May 23, 2013
• 年：2013
• 卷：117
• 期：20
• 页码：10326-10335
• 全文大小：567K
• 年卷期：v.117,no.20(May 23, 2013)
• ISSN：1932-7455

文摘

Zeolitic imidazolate framework (ZIF) materials have received considerable attention recently due to their potential as materials for gas separation applications. In this work, we study, both experimentally and with molecular modeling, methane adsorption in a series of five ZIFs (ZIF-25, -71, -93, -96, and -97) that share a common structural topology (RHO), but differ in imidazolate functionalization. Such a series allows for the direct assessment of the role that functionalization plays in determining methane adsorption. Experimental measurements of methane adsorption up to 1 bar at various temperatures are well reproduced by molecular simulations, which are further used to examine adsorption up to higher pressures of 80 bar, and to analyze the preferred binding sites within the structure. We find that CH₄ uptake in these ZIFs is roughly proportional to the Brunauer鈥揈mmett鈥揟eller (BET) surface area, in contrast to our earlier work on the adsorption of CO₂ for this series [J. Am. Chem. Soc.2010, 132, 11006], which showed a significant enhancement of CO₂ adsorption, due to electrostatic effects, in asymmetrically functionalized ZIFs (ZIF-93, -96, -97) over those with symmetric functionalization (ZIF-25, -71). Furthermore, the ideal adsorbed solution theory (IAST) is used to predict selectivity of CO₂ over CH₄ in these RHO ZIFs by fitting CH₄ adsorption measurements in this work and the CO₂ experimental isotherms from our earlier work [J. Am. Chem. Soc.2010, 132, 11006].