Ionic liquid functionalized covalent organic framework membranes for efficient CO2/N2 separation

Covalent organic framework (COF) materials exhibit considerable potential for membrane separation applications due to their long-range ordered pore structures, tunable pore chemical microenvironments, and excellent thermochemical stability. However, the intrinsic pore sizes of COF materials often exceed the kinetic diameters of target gas molecules, thereby limiting their efficacy in gas separation. In this study, we present a strategy for the functionalization of ionic COF nanosheets using ionic liquids. The immobilization of ionic liquids within the pores and interlayers of ionic COF nanosheets was accomplished through a straightforward physical blending method, which leverages the electrostatic interactions between the abundant charged groups from the ionic COF nanosheets and the ionic liquids. Subsequently, we prepared CO 2 separation membranes with a thickness of less than 100 nm. The resulting COF membranes demonstrated excellent separation performance with a CO 2 permeance of up to 1116 GPU and a CO 2 /N 2 selectivity of 20.3 as well as good stability. This study offers a simple and effective approach for developing high-performance COF membranes for carbon capture.