On competitive gas adsorption and absorption phenomena in thin films of ionic liquids
On competitive gas adsorption and absorption phenomena in thin films of ionic liquids
复制标题
DOI：
10.1039/d0ta03419c
复制
发表时间：
2020-06-21
影响因子：
11.9
通讯作者：
Sarkisov, Lev
中科院分区：
文献类型：
--
作者：
Lapshin, Dmitry N.;Jorge, Miguel;Sarkisov, Lev
尽管人们对在多孔材料表面上具有离子液体薄膜的材料产生了很大的兴趣，但仍然缺乏对气液界面过程的基本理解，阻碍了新型吸附剂和吸附模型的开发。本文研究了离子液体[BMIM]（+）[PF6]（-）在含CO2和N2的气相中的竞争吸附机理。为了正确估计这些过程的定量贡献，我们进行了经典的分子动力学模拟的气-液界面系统。气体的吸附通过在离子液体的表面上形成吸附的气体层和气体在本体液相中的部分溶解来进行。为了表征这两个过程之间的竞争，我们引入了一个参数，离子液体的膜的均分厚度，它涉及的贡献溶解在液相中的气体和吸附在膜的表面上的气体的总吸附量。在给定的温度下，对于亨利定律体系中的特定气体-离子液体对，均分厚度是恒定的，其中吸收与施加的气体压力成比例。通过计算和现有的实验研究相结合，我们提出了如何一个单一的属性，均分厚度，可以管理特定任务的多孔材料的发展，并预测其性能以及气体吸附热力学。
Although there has been a lot of interest in materials that feature thin films of ionic liquids on the surface of porous materials, fundamental understanding of gas-liquid interfacial processes is still lacking, hindering the development of novel adsorbents and adsorption models for practical applications. Herein, we investigated the mechanism of competitive gas adsorption on and absorption in thin films of ionic liquid, [BMIM](+)[PF6](-), exposed to the gas phase containing carbon dioxide and nitrogen. To estimate correct quantitative contributions of these processes, we performed classical molecular dynamics simulations of the gas-liquid interfacial systems. Adsorption of gases proceeds through the formation of an adsorbed gas layer on the surface of the ionic liquid and partial dissolution of the gas in the bulk liquid phase. To characterize the competition between these two processes we introduced a parameter, the equipartition thickness of the film of ionic liquid, which relates the contributions of gas dissolved in the liquid phase and gas adsorbed on the surface of the film to the total amount adsorbed. At a given temperature, the equipartition thickness is constant for a specific gas-ionic liquid pair in the Henry's law regime, where uptake is proportional to the applied gas pressure. Through the combination of computational and available experimental studies, we propose how a single property, the equipartition thickness, may govern the development of task-specific porous materials and predict their performance as well as thermodynamics of gas adsorption.