Sealing functional ionic liquids in conjugated microporous polymer membrane by solvent-assisted micropore tightening

Porous organic polymers hold great promise for molecular sieving membrane separation. Although the inclusion of functional ionic liquid (IL) in the pores offers a facile way to manipulate their separation properties, the IL leaching during the separation process is difficult to avoid. Herein, we report a strategy to in-situ encapsulate ILs into the micropores of the conjugated microporous polymer membrane via a 6-min electropolymerization and further seal the aperture of the pores to prevent ILs leaching by solvent-assisted micropore tightening (SAMT). Upon screening the binding energy between different ILs and gas molecules, two ILs were selected to be incorporated into the membrane for CO2/CH4 and O2/N2 gas separations. The resultant separation performances surpass the 2008 Robeson upper bound. Notably, the ILs can be locked in the micropores by a facile high surface tension solvent treatment process to improve their separation stability, as evidenced by a 7-day continuous test. This simple and controllable process not only enables efficient and steady separation performance but also provides an effective strategy for confining and sealing functional guest molecules in the porous solids for various applications.