Scalable and interfacial gap‐free mixed matrix membranes for efficient anion separation

Abstract Mixed matrix membranes (MMMs) are promising in ion separation due to the simple preparation process. However, traditional metal–organic framework and covalent organic framework fillers lack the solution processibility and show interfacial defects between polymer matrixes and fillers, resulting in unsatisfactory separation performance. Herein, a soluble porous organic cage (POC) (i.e., CC3) is used as the filler to fabricate a large scale (~2000 cm 2 ) and interfacial gap‐free ionic polymer (HPABP)‐CC3 membrane by a facile co‐solvent casting and rapid crystallization method. The resultant HPABP‐CC3(15) membrane shows a high Cl − flux of 2.24 mol m −2 h −1 and a Cl − /SO 4 2− selectivity of 12.67, which is 3.6 and 3.0 times that of the HPABP membrane, respectively. Moreover, the HPABP‐CC3 membranes possess excellent cyclic and long‐term stability during the electrodialysis process. Therefore, we provide a facile strategy to scale up POC MMMs with synergistically enhanced ion flux and selectivity and the possibility for potential industrial ion separations.