An Ionic Covalent Organic Framework Membrane with Confined Mobile Carriers for Stable and Efficient Carbon Dioxide Capture

Membrane-based postcombustion carbon capture is a promising method for reducing carbon dioxide (CO2) emissions. Mobile carrier-facilitated transport membranes (FTMs) are receiving attention because they can simultaneously increase CO2 permeability and CO2/N2 selectivity. However, FTMs still face the challenge of carrier loss. Stable immobilization of mobile carriers is essential for achieving and maintaining superior separation performance of FTMs. Herein, we report an ionic covalent organic framework (COF) membrane with confined mobile carriers for stable and efficient CO2 separation. In this structure, a typical CO2 mobile carrier, 2,5-diethylenetriamine (DETA), is stabilized in the negatively charged nanochannels of the COF membrane. Thanks to the intrinsic CO2-facilitated transport of DETA, the COF membrane presents a CO2 permeance of 2347 GPU and a CO2/N2 selectivity of 191 under simulated flue gas conditions. Because the CO2 mobile carriers are firmly confined within the pores through electrostatic interactions, the membrane shows stable separation performance during the 310 h continuous test. The excellent performance and robust stability demonstrate the significant potential of this innovative membrane structure for practical use in the capture of CO2 from flue gas.