Diffusion of CH4 in ZIF-8 Studied by Quasi-Elastic Neutron Scattering
Diffusion of CH4 in ZIF-8 Studied by Quasi-Elastic Neutron Scattering
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DOI：
10.1021/acs.jpcc.5b04259
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发表时间：
2015-07-16
影响因子：
3.7
通讯作者：
Ollivier, J.
中科院分区：
文献类型：
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作者：
Jobic, H.;Kolokolov, D. I.;Ollivier, J.
准弹性中子散射 (QENS) 测量已在分子水平上表征 ZIF-8 中不同浓度吸附的 CH4 的扩散。这使得首次能够比较通过微观和介观技术在 MOF 中获得的扩散率。不同方法之间观察到的良好一致性表明不存在阻碍扩散的缺陷，而沸石中经常出现这种情况。即使ZIF-8窗口的有效尺寸大于晶体学得出的直径，笼间扩散的特征时间（类似于ns）也比笼内跳跃之间的时间（类似于10 ps）长得多，这表明有机连接体严重阻碍了分子通过。
Quasi-elastic neutron scattering (QENS) measurements have been performed to characterize at the molecular level the diffusion of CH4 adsorbed at various concentrations in ZIF-8. This allows to compare for the first time diffusivities obtained in a MOF by microscopic and mesoscopic techniques. The good agreement which is observed between the different methods shows that there are no defects obstructing diffusion, which is often the case in zeolites. Even if the effective size of ZIF-8 windows is larger than the diameter derived from crystallography, the characteristic time for intercage diffusion (similar to ns) is much longer than the time between jumps within a cage (similar to 10 ps), indicating that the organic linkers severely hinder molecule passage.