Zhang Kuiyuan, Zhou Lixia, Wang Zichang, Li Haiyang, Yan Youguo, Zhang Jun
School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao 266000, P. R. China.
College of Science, China University of Petroleum, Qingdao 266000, P. R. China.
Phys Chem Chem Phys. 2022 Oct 5;24(38):23690-23698. doi: 10.1039/d2cp03044f.
The covalent organic framework (COF) shows great potential for use in gas separation because of its uniform and high-density sub-nanometer sized pores. However, most of the COF pore sizes are large, and there are mismatches with the gas pairs (3-6 Å), and the steric hindrance cannot work in gas selectivity. In this work, one type of COF (NUS-2) supported ionic liquid membrane (COF-SILM) was prepared for use in CO/N separation. The separation performance was investigated using molecular dynamics simulation. There was an ultrahigh CO permeability up to 2.317 × 10 GPU, and a better CO selectivity was obtained when compared to that of N. The physical mechanism of ultrahigh permeability and CO selectivity are discussed in detail. The ultrathin membrane, high-density pores and high transmembrane driving force are responsible for the ultrahigh permeability of CO. The different adsorption capabilities of ionic liquid (IL) for CO and N, as well as a gating effect, which allows CO passage and inhibits N passage, contribute to the better CO selectivity over N. Moreover, the effects of the COF layer number and IL thickness on gas separation performance are also discussed. This work provides a molecular level understanding of the gas separation mechanism of COF-SILM, and the simulation results show one potential outstanding CO separation membrane for future applications.
共价有机框架（COF）由于其均匀且高密度的亚纳米级孔隙，在气体分离方面显示出巨大的应用潜力。然而，大多数COF的孔径较大，与气体对（3 - 6 Å）存在不匹配，空间位阻在气体选择性方面无法发挥作用。在这项工作中，制备了一种用于CO/N分离的COF（NUS-2）负载离子液体膜（COF-SILM）。使用分子动力学模拟研究了其分离性能。获得了高达2.317×10 GPU的超高CO渗透率，与N相比，CO选择性更好。详细讨论了超高渗透率和CO选择性的物理机制。超薄膜、高密度孔隙和高跨膜驱动力导致了CO的超高渗透率。离子液体（IL）对CO和N的不同吸附能力以及允许CO通过而抑制N通过的门控效应，使得CO对N具有更好的选择性。此外，还讨论了COF层数和IL厚度对气体分离性能的影响。这项工作提供了对COF-SILM气体分离机制的分子水平理解，模拟结果表明其是一种未来应用中潜在的优秀CO分离膜。
