Solubility and diffusivity of CO2 in ionic polyimides with [C(CN)3]x[oAc]1−x anion composition
Solubility and diffusivity of CO2 in ionic polyimides with [C(CN)3]x[oAc]1−x anion composition
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DOI：
10.1016/j.commatsci.2019.109468
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发表时间：
2020-03
影响因子：
3.3
通讯作者：
J. Szala-Bilnik;Ellis R. Crabtree;A. Abedini;J. Bara;C. Turner
中科院分区：
文献类型：
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作者：
J. Szala-Bilnik;Ellis R. Crabtree;A. Abedini;J. Bara;C. Turner
近年来，含有乙酸[oAc−]和三氰甲烷[C(CN)3−]阴离子的混合离子液体（ILs）已被证明具有良好的溶剂和co2吸附剂的特性。通过对阴离子组成进行优化，可以显著提高扩散率，同时只略微降低溶解度。在这里，我们探索应用于离子聚酰亚胺（i-PI）材料的类似研究，以了解当使用聚合物材料时出现的分子水平动力学和热力学特征。所研究的i-PI系统是一类新兴的“高性能”离子烯聚合物的一部分，在气体分离膜中具有巨大的应用潜力。本文采用分子动力学（MD）和大规范蒙特卡罗（GCMC）模拟相结合的方法，模拟了具有不同浓度的[oAc−]和[C(CN)3−]两个反阴离子的整齐i-PI体系。较高浓度的[C(CN)3−]可以改善co 2的扩散，类似于纯IL的性能，而溶解度保持相对不变。i-PI系统的结构特征提供了阴离子对吸附性能的影响的详细见解。溶解度与理论表面积的关系较弱，而扩散率与分数自由体积（FFV）的关系中等。总的来说，不同阴离子的组合被预测为提高i-PI材料的扩散率的可行策略，但纯il的行为不能简单地推断为膜中的离子行为。
Recently, mixtures of ionic liquids (ILs) containing acetate [oAc−] and tricyanomethanide [C(CN)3−] anions have demonstrated promising characteristics as solvents and as CO2adsorbents. The anion composition can be optimized to obtain a significant improvement in the diffusivity while only slightly decreasing the solubility. Here, we explore a similar investigation applied to an ionic polyimide (i-PI) material in order to understand the molecular-level kinetic and thermodynamic characteristics that emerge when a polymeric material is used instead. The i-PI systems studied are part of an emerging class of “high-performance” ionene polymers that hold significant potential for applications in gas separation membranes. Here, neat i-PI systems with the two counter anions, [oAc−] and [C(CN)3−], at varying concentrations are modeled by a combination of molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) simulations. Higher concentrations of [C(CN)3−] are predicted to improve CO2diffusion, similar to the pure IL performance, while solubility remains relatively unchanged. The structural characteristics of the i-PI systems provide detailed insight into the effect that the anions have on the adsorption properties. The solubility is weakly related to the theoretical surface area, and the diffusivity is moderately correlated to the fractional free volume (FFV). Overall, the combination of different anions is predicted to be a viable strategy for improving the diffusivity throughout i-PI materials, but the behavior of pure ILs cannot be simply extrapolated to ion behavior in membranes.