Why is the partial molar volume of CO2 so small when dissolved in a room temperature ionic liquid?: Structure and dynamics of CO2 dissolved in [Bmim+] [PF6-]
Why is the partial molar volume of CO2 so small when dissolved in a room temperature ionic liquid?: Structure and dynamics of CO2 dissolved in [Bmim+] [PF6-]
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DOI：
10.1021/ja055315z
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发表时间：
2005-12-21
影响因子：
15
通讯作者：
Berne, BJ
中科院分区：
文献类型：
--
作者：
Huang, XH;Margulis, CJ;Berne, BJ
当超临界CO2溶解在离子液体中时，其偏摩尔体积远小于在大多数其他溶剂中观察到的偏摩尔体积。在这篇文章中，我们探索原子的细节，并解释在一个直观的方式实验观察到的特殊的体积行为时，超临界CO2溶解在1-丁基-3-甲基咪唑六氟磷酸盐（[Bmim（+）] [PF 6-]）。我们还提供了物理洞察的结构和动力学发生在整个边界的CO2离子液体界面。我们发现，即使在相当大的CO2摩尔分数下，[Bmim+] [PF 6-]在CO2存在下的液体结构与纯离子液体（IL）中的液体结构几乎相同。我们的模拟表明，与实验一致，一种流体进入另一种流体的部分亲合性是非常不对称的，CO2在离子液体相中高度可溶，而离子液体在CO2相中高度不溶。我们解释我们的结果在离子液体相自发形成的空腔的大小和形状方面，我们提出，CO2占据非常明确的位置在IL。尽管我们对纯IL中空腔尺寸的准确预测表明，与单个碳原子或氧原子的货车范德华半径相比，这些空腔很小，但CO2似乎占据了一个大部分先验“空”的空间。
When supercritical CO2 is dissolved in an ionic liquid, its partial molar volume is much smaller than that observed in most other solvents. In this article we explore in atomistic detail and explain in an intuitive way the peculiar volumetric behavior experimentally observed when supercritical CO2 is dissolved in 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim(+)] [PF6-]). We also provide physical insight into the structure and dynamics occurring across the boundary of the CO2 ionic liquid interface. We find that the liquid structure of [Bmim+] [PF6-] in the presence Of CO2 is nearly identical to that in the neat ionic liquid (IL) even at fairly large mole fractions Of CO2- Our simulations indicate, in agreement with experiments, that partial miscibilities of one fluid into the other are very unsymmetrical, CO2 being highly soluble in the ionic liquid phase while the ionic liquid is highly insoluble in the CO2 phase. We interpret our results in terms of the size and shape of spontaneously forming cavities in the ionic liquid phase, and we propose that CO2 occupies extremely well-defined locations in the IL. Even though our accurate prediction of cavity sizes in the neat IL indicates that these cavities are small compared with the van der Waals radius of a single carbon or oxygen atom, CO2 appears to occupy a space that was for the most part a priori "empty".