Adsorption Characteristics of Metal鈥揙rganic Frameworks Containing Coordinatively Unsaturated Metal Sites: Effect of Metal Cations and Adsorbate Properties

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• 作者：Prashant Mishra ; Satyannarayana Edubilli ; Bishnupada Mandal ; Sasidhar Gumma
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：April 3, 2014
• 年：2014
• 卷：118
• 期：13
• 页码：6847-6855
• 全文大小：505K
• 年卷期：v.118,no.13(April 3, 2014)
• ISSN：1932-7455

文摘

Metal鈥搊rganic frameworks in the M/DOBDC series are known to contain a large number of coordinatively unsaturated metal (M) sites. In this work, we study the influence of various metal cations (M = Mg, Mn, Co, and Ni) in the framework on its gas adsorption characteristics. The probe gases (viz. CO₂, CO, CH₄, C₂H₆, N₂, and Ar) were carefully chosen to cover a wider range of polarity and polarizability. While a significant impact of metal atom in the framework is observed on adsorption of polar gases such as CO₂ and CO, it has a negligible effect on adsorption of other relatively nonpolar gases. On one hand, Henry鈥檚 constant of CO₂ for Mg/DOBDC is about 4鈥?0 times higher than that for other frameworks; on the other, Henry鈥檚 constant for CO on Ni/DOBDC is about 100 times larger than that on Mn/DOBDC. The pore volume of the framework governs adsorption capacity at higher pressures. Each of the frameworks exhibits widely different adsorption enthalpies for polar gases such as CO₂ and CO. At pressures below 15 bar, the Ideal Adsorbed Solution Theory predicts very good selectivity for CO over all other studied gases on Ni and Co/DOBDC frameworks, while Mg and Mn/DOBDC frameworks exhibit preferential selectivity for CO₂.