Guest Controlled Rotational Dynamics of Terephthalate Phenylenes in Metal鈥揙rganic Framework MIL-53(Al): Effect of Different Xylene Loadings

详细信息    查看全文

• 作者：Daniil I. Kolokolov ; Alexander G. Stepanov ; Herv茅 Jobic
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：July 24, 2014
• 年：2014
• 卷：118
• 期：29
• 页码：15978-15984
• 全文大小：311K
• ISSN：1932-7455

文摘

MIL-53 is an interesting metal鈥搊rganic framework (MOF) with a 鈥渂reathing鈥?framework which is envisioned for a number of potential applications. It is suggested that the processes of hydrocarbon adsorption, diffusion, and separation by this material are strongly influenced by flexibility of the framework and fastly moving terephthalate phenylene fragments, representing the array of molecular rotors. To govern the mentioned processes we need to learn how to monitor the flexibility of the framework and identify the specific effects of particular hydrocarbons on the rotational motion of phenylene fragments. Here we demonstrate that flexibility, i.e., large pore (LP) and narrow pore (NP) crystalline state interconversions of the framework, can be monitored by following the evolution of phenylene fragments dynamics with temperature by ²H solid-state nuclear magnetic resonance. We have established that the dynamics of phenylene fragments is very sensitive to the loading of xylene guests and the MOF structural state. The rotation rate is higher and the activation barrier lower for the LP state of the guest-free or loosely loaded material, whereas the NP and LP states with high loadings and dense guest packing show a decrease of the rotation rates and increase of the rotation energetic barrier.