Molecular motions taking place in the nanospace of metal–organic frameworks (MOFs) are an interesting research subject, although not yet fully investigated. In this work, we utilized in situ Raman spectroscopy in the ultralow-frequency region to investigate the libration motion (including the rotational motion of phenylene rings) of MOFs, in particular [Cu₂(bdc)₂(dabco)] (Cu-JAST-1), where bdc = 1,4-benzenedicarboxylate and dabco = 1,4-diazabicyclo[2.2.2]octane. The libration mode of Cu-JAST-1 was found to be significantly suppressed by the adsorption of various guest molecules, such as CO₂, Ar, and N₂. In addition, an appreciable correlation between the libration mode and adsorption equilibrium time was identified, which provides useful novel tools in the design of MOFs acting as molecular adsorption and separation materials.

中文翻译：

---

原位拉曼光谱研究气体吸附MOFs在纳米空间中的分子运动

在金属-有机骨架（MOFs）的纳米空间中发生的分子运动是一个有趣的研究主题，尽管尚未进行充分研究。在这项工作中，我们利用原位拉曼光谱在超低频率区域进行调查的MOF的释出运动（包括亚苯基环的旋转运动），特别是[铜₂（BDC）₂（DABCO）]法（Cu-JAST -1），其中bdc = 1,4-苯二羧酸酯，而dabco = 1,4-二氮杂双环[2.2.2]辛烷。发现通过吸附各种客体分子（例如CO ₂，Ar和N _2）显着抑制了Cu-JAST-1的释放模式。此外，还确定了释放模式与吸附平衡时间之间存在明显的相关性，这为设计用作分子吸附和分离材料的MOF提供了有用的新颖工具。