Enthalpic Driving Force for the Selective Absorption of CO2 by an Ionic Liquid,The Journal of Physical Chemistry Letters

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Enthalpic Driving Force for the Selective Absorption of CO2 by an Ionic Liquid
The Journal of Physical Chemistry Letters ( IF 4.8 ) Pub Date : 2018-03-05 00:00:00 , DOI: 10.1021/acs.jpclett.8b00347
Clyde A. Daly ₁ , Thomas Brinzer _{2,

3} , Cecelia Allison ₁ , Sean Garrett-Roe _{2,

3} , Steven A. Corcelli ₁

Affiliation

Molecular dynamics (MD) simulations validated against two-dimensional infrared (2D-IR) measurements of CO₂ in an imidazolium-based ionic liquid have revealed new insights into the mechanism of CO₂ solvation. The first solvation shell around CO₂ has a distinctly quadrupolar structure, with strong negative charge density around the CO₂ carbon atom and positive charge density near the CO₂ oxygen atoms. When CO₂ is modeled without atomic charges (thus removing its strong quadrupole moment), its solvation shell weakens and changes significantly into a structure that is similar to that of N₂ in the same liquid. The solvation shell of CO₂ evolves more quickly when its quadrupole is removed, and we find evidence that solvent cage dynamics is measured by 2D-IR spectroscopy. We also find that the solvent cage evolution of N₂ is similar to that of CO₂ with no atomic charges, implying that the weaker quadrupole of N₂ is responsible for its higher diffusion and lower absorption in ionic liquids.

中文翻译：

离子液体选择性吸收CO ₂的焓驱动力

针对基于咪唑鎓离子液体的CO ₂的二维红外（2D-IR）测量验证的分子动力学（MD）模拟，揭示了对CO ₂溶剂化机理的新见解。围绕CO所述第一溶剂化壳₂有一个明显的四极结构，与周围的CO强的负电荷密度₂碳原子和正电荷密度的CO附近₂个氧原子。如果在没有原子电荷的情况下对CO ₂进行建模（从而消除了其强大的四极矩），则其溶剂化壳会减弱并显着改变为类似于同一液体中N ₂的结构。CO ₂的溶剂化壳除去四极杆后，其演化更快，我们发现有证据表明溶剂笼动力学是通过2D-IR光谱法测量的。我们还发现，N ₂的溶剂笼演化与无原子电荷的CO ₂相似，这表明N _2的四极分子较弱是其在离子液体中的较高扩散和较低吸收的原因。

更新日期：2018-03-05

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