Ionic liquid gated 2D-CAP membrane for highly efficient CO2/N2 and CO2/CH4 separation

Recently, a two-dimensional conjugated aromatic polymer (2D-CAP) membrane has been synthesized, and it shows promising applications in the selected gas separation. However, the sub-nanometer pores of the 2D-CAP membrane are relatively large compared with small gas molecules like CO2, N-2, and CH4, which impedes the efficiency of the gas separation. Here, we report a strategy to improve the gas separation performance of 2D-CAP membranes. Specifically, coating ultra-thin ionic liquid (IL) onto the 2D-CAP membrane was found to well harmonize the pore size of 2D-CAP membranes. In this work, the gas separation performance of this 2D-CAP supported IL membrane (2D-CAP SILM) was investigated using molecular dynamics simulations. An ultrahigh CO2 permeance of similar to 10(5) GPU, which is larger than many reported theoretically predicted results, was exhibited. Meanwhile, an excellent selectivity of CO2/N-2 and CO2/CH4 beyond 40 was obtained. The ultrathin membrane and the high-density pore are responsible for the high gas permeance, and the selectivity could be ascribed to IL adsorption selectivity of CO2 over N-2/CH4 and a fascinating gating effect that anion of IL ([BF4](-)) suspending upside the pore center allows CO2 passage while prohibits N-2/CH4 passage. The present work suggests a promising membrane for practical highly efficient CO2 separation.