Enthalpic effects in the adsorption of alkylaromatics on the metal-organic frameworks MIL-47 and MIL-53

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• 作者：Michael Maes^a ; Frederik Vermoortele^a ; Mohammed Boulhout^b ; Tom Boudewijns^a ; Christine Kirschhock^a ; Rob Ameloot^a ; Isabelle Beurroies^b ; Renaud Denoyel^b ; Dirk E. De Vos^a ; ^{dirk.devos@biw.kuleuven.be}
• 关键词：Adsorption ; Calorimetry ; Metal-organic framework ; MIL-53 ; MIL-47
• 刊名：Microporous and Mesoporous Materials
• 出版年：2012
• 期刊代码：78_13871811
• 类别：ch
• 出版时间：15 July, 2012
• 卷：157
• 期：Complete
• 页码：82-88
• 文件大小：622 K

摘要

This work reports on the adsorptive separation of mono- and disubstituted alkylaromatics with various alkyl groups in the microporous metal-organic frameworks MIL-47 (V^IVO{O₂C-C₆H₄-CO₂}) and MIL-53 (Al^III(OH){O₂C-C₆H₄-CO₂}). The mechanisms underlying the adsorption selectivity are investigated via determination of the adsorption enthalpies at low or high loading, either via pulse chromatographic or calorimetric methods. Results of both methods are in fair agreement. It is shown that the strong preference of MIL-47 for n-propylbenzene over cumene is due to a more favorable adsorption enthalpy. In addition, upon adsorbing n-alkylbenzenes with increasing alkyl chain length a stepwise increase in adsorption enthalpy is observed, which possibly indicates the importance of alkyl chain length in spanning the distance between adjacent, regularly spaced interaction sites in the crystal lattice. Finally, we also study the adsorption enthalpies of various xylene isomers and ethylbenzene on MIL-47 and MIL-53. It is found that enthalpic as well as entropic effects play an important role in determining the adsorption selectivity.