化学
位阻效应
金属有机骨架
背景(考古学)
分子动力学
绕固定轴旋转
化学物理
放松(心理学)
结晶学
计算化学
立体化学
物理化学
物理
心理学
古生物学
社会心理学
吸附
经典力学
生物
作者
Stephanie L. Gould,David J. Tranchemontagne,Omar M. Yaghi,Miguel A. Garcı́a-Garibay
摘要
Metal−organic frameworks (MOFs) have been the focus of much interest within the context of hydrogen storage and other materials applications. With static metal clusters linked by axially substituted organic spacers capable of experiencing internal rotations, MOFs are one of the most promising amphidynamic materials to investigate and exploit the dynamics of crystalline solids. In this communication we report an experimental study of the rotational dynamics of the 1,4-phenylenedicarboxylate bridge of MOF-5, which has no steric contacts that might contribute to the rotational barrier. Highly reproducible 1H T1 relaxation, high-resolution 13C CPMAS, and variable temperature quadrupolar echo 2H NMR data were obtained from high quality samples that were sealed at reduced pressure (ca. 3 mTorr). 2H NMR line shape simulation revealed an activation barrier for rotation of 11.3 ± 2.0 kcal/mol, which is lower than the 14−16 kcal/mol values reported in theoretical studies of truncated models. While our results suggest that the models used for MOF-5 are insufficient to account for the properties of the extended crystal lattice, they also suggest that the amphidynamic materials with static and dynamic components may reach the friction-free rotational motion characteristic of gas dynamics.
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