High-Pressure in Situ 129Xe NMR Spectroscopy and Computer Simulations of Breathing Transitions in the Metal鈥揙rganic Framework Ni2(2,6-ndc)2(dabco) (DUT-8(Ni))

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• 作者：Herbert C. Hoffmann ; Bassem Assfour ; Fanny Epperlein ; Nicole Klein ; Silvia Paasch ; Irena Senkovska ; Stefan Kaskel ; Gotthard Seifert ; Eike Brunner
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：June 8, 2011
• 年：2011
• 卷：133
• 期：22
• 页码：8681-8690
• 全文大小：1066K
• 年卷期：v.133,no.22(June 8, 2011)
• ISSN：1520-5126

文摘

Recently, we have described the metal鈥搊rganic framework Ni₂(2,6-ndc)₂(dabco), denoted as DUT-8(Ni)(1) (DUT = Dresden University of Technology, 2,6-ndc = 2,6-naphthalenedicarboxylate, dabco = 1,4-diazabicyclo[2.2.2]octane). Upon adsorption of molecules such as nitrogen and xenon, this material exhibits a pronounced gate-pressure effect which is accompanied by a large change of the specific volume. Here, we describe the use of high-pressure in situ ¹²⁹Xe NMR spectroscopy, i.e., the NMR spectroscopic measurements of xenon adsorption/desorption isotherms and isobars, to characterize this effect. It appears that the pore system of DUT-8(Ni) takes up xenon until a liquid-like state is reached. Deeper insight into the interactions between the host DUT-8(Ni) and the guest atom xenon is gained from ab initio molecular dynamics (MD) simulations. van der Waals interactions are included for the first time in these calculations on a metal鈥搊rganic framework compound. MD simulations allow the identification of preferred adsorption sites for xenon as well as insight into the breathing effect at a molecular scale. Grand canonical Monte Carlo (GCMC) simulations have been performed in order to simulate adsorption isotherms. Furthermore, the favorable influence of a sample pretreatment using solvent exchange and drying with supercritical CO₂ as well as the influence of repeated pore opening/closure processes, i.e., the 鈥渁ging behavior鈥?of the compound, can be visualized by ¹²⁹Xe NMR spectroscopy.