二维层状材料支撑离子液体膜的限域传质机制及高效气体分离

High efficient CO2 separation and capture is very important to reduce the "Greenhouse Effect". Due to their unique physic and chemical properties and atomic thick sheet structures, two-dimensional (2D) materials are promising for the construction of novel gas separation membranes. Recently, it has been reported that water could dramatically enhance the CO2 separation performance of graphene oxide membranes. However, water is very easily to be lost during the gas separation, especially at relatively high temperature and processed for long time. This will significantly degrade the separation performance. In order to solve this problem, in this project, we will combine nonvolatile, thermal stable, high CO2 solubility and tunable functionalities of ionic liquid and the unique properties of 2D materials to develop high thermal stability, long life time, and high efficient 2D materials supported ionic liquid CO2 separation membranes. We will focus on the following contents: (1) The interaction between ionic liquid and 2D material layers and the surface wetting ability will be studied in detail. Then we will develop novel methods to introduce ionic liquid into the nanospace of the laminated 2D nanosheets thin films to obtain 2D layered thin film supported ionic liquid separation membranes; (2) The properties of ionic liquids confined in 2D materials constructed nanospace with different sizes and surface properties, and the corresponding gas transportation and separation performances will be systematically investigated. (3) Base on the experiment results and theoretical analysis and simulation, the original of the interaction and transportation behavior will be clarified. We will establish the corresponding theoretical mass-transportation model, and develop methods to modify and control the properties of the 2D materials nanochannels. Then, long duration, high temperature stable, and high efficient 2D materials supported ionic liquid CO2 separation membranes will be obtained. This project will provide new membrane materials and techniques for separation and capture of CO2.

CO2的高效分离与捕获是减少“温室效应”的有效途径。二维层状材料在构筑高效气体分离膜方面具有诱人前景。最近报道水可极大提高氧化石墨烯膜对CO2的分离效率。但水易挥发，热稳定性差，这严重阻碍了其实际应用。为解决此问题，本项目将利用不易挥发、热稳定、高CO2溶解度的离子液体代替水制备出二维层状材料支撑离子液体高效CO2分离膜。主要研究内容为：（1）研究离子液体与二维层状材料表/界面相互作用、浸润特性，发展将离子液体引入二维层状材料纳米孔道的有效方法，获得二维层状材料支撑离子液体膜；（2）研究离子液体在不同孔道尺寸及表面性质的二维层状材料受限孔道中的热力学性质及其对CO2分离性能的影响规律；（3）结合理论计算与模拟揭示其限域传质机制，建立相应的理论模型，掌握孔道构筑和调变技术，实现较高温、长时间稳定高效的二维层状材料支撑离子液体CO2分离膜的制备，为 CO2的高效分离与捕获提供新的膜材料和技术。

为解决水润湿二维材料分离膜中水易挥发，热稳定性差，长时间或较高温度下使用水易流失的问题。本项目将不易挥发、热稳定、高粘度、功能可调特性的离子液体引入二维层状材料构筑的纳米孔洞中制备二维片层材料支持的离子液体膜。（1）发现了二维受限空间中的离子液体阴阳离子分层有序分布现象，基于理论计算，该分布可有效降低阴阳离子相互作用、提高自由体积、选择性增加二氧化碳的溶解度，进而显著提高二氧化碳的选择性传输及膜的稳定性。（2）创新性的通过施加电场调控二维离子液体膜的气体分离性能。揭示了电场可进一步导致离子液体的阴阳离子分层、增加自由体积、提高CO2的溶解度，从而在提高CO2通量1倍的同时实现分离比提高5倍。这些为高效液体及气体分离膜的设计与开发提供了支撑。