Wang Huijie, Huan Shuang, Chu Zhenyu, Yin Zongyou, Wang Chen
State Key Laboratory of Microbial Technology, Jiangsu Collaborative Innovation Center of Biomedical Functional Materials, Jiangsu Key Laboratory of New Power Batteries, School of Chemistry and Materials Science, Nanjing Normal University Nanjing 210023 China
State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University Nanjing 211816 China.
Chem Sci. 2025 Sep 16. doi: 10.1039/d5sc04964d.
Conventional nanofluidic membranes often exhibit low selectivities for efficient separation of gases with similar kinetic diameters. Soft nanofluidic membranes overcome this challenge through a combination of selective binding sites and tunable pore structures, creating an on-demand separation switch that enables adaptive pore opening for enhanced gas separation. Herein, three different nanofluidic membranes of soft covalent organic frameworks (named S-COF1, S-COF2, and S-COF3) with varied flexibility levels were synthesized for similar-sized gas separation using ethane (CH) and ethylene (CH) as model gases. The flexibility was precisely tuned by introducing varying numbers of functionalized -OH linkers to form intramolecular [-O-H⋯N[double bond, length as m-dash]C] hydrogen bonding. Highly flexible S-COF1 and S-COF2 demonstrated similar pore behavior for CH and CH, resulting in poor separation efficiency. In contrast, S-COF3, with enhanced rigidity due to the addition of the highest amount of -OH linkers, exhibited distinct pore switching from "close" in CH to "open" in CH. This led to a CH/CH selectivity of 18.2, which is superior to that of most of the reported membranes. This work establishes a functionalized -OH linker strategy to precisely tune COF flexibility, revealing its critical role in gas separation and advancing the design of dynamic porous membranes.
传统的纳米流体膜在有效分离具有相似动力学直径的气体时，往往表现出较低的选择性。软纳米流体膜通过选择性结合位点和可调孔结构的组合克服了这一挑战，创造了一种按需分离开关，能够实现自适应孔开放以增强气体分离。在此，合成了三种具有不同柔韧性水平的软共价有机框架纳米流体膜（命名为S-COF1、S-COF2和S-COF3），以乙烷（CH）和乙烯（CH）作为模型气体用于类似尺寸气体的分离。通过引入不同数量的功能化-OH连接体形成分子内[-O-H⋯N[双键，长度为m破折号]C]氢键来精确调节柔韧性。高度柔性的S-COF1和S-COF2对CH和CH表现出相似的孔行为，导致分离效率较差。相比之下，由于添加了最多量的-OH连接体而具有更高刚性的S-COF3，表现出从CH中的“关闭”到CH中的“开放”的明显孔切换。这导致CH/CH选择性为18.2，优于大多数已报道的膜。这项工作建立了一种功能化-OH连接体策略来精确调节COF的柔韧性，揭示了其在气体分离中的关键作用，并推动了动态多孔膜的设计。
