Novel polymers of intrinsic microporosity-based anion exchange membranes with high performance and robust stability for diffusion dialysis acid recovery

The development of anion exchange membranes (AEMs) that synergistically combine high performance with robust stability is essential for optimizing diffusion dialysis (DD) acid recovery. In response to this need, we introduce a novel strategy employing bromomethylated polymers of intrinsic microporosity (PIM-Br), pre-crosslinked with pentamethyldiethylenetriamine (PMDETA), followed by subsequent simultaneous crosslinking and cationization with 4,4′-bipyridine (BPY). This approach results in AEMs with expansive free volume (specific surface area = 163.55 m 2  g −1 ), high mechanical strength (tensile stress = 22.14 MPa), and exceptional resistance to both acidic environments and organic solvents, thereby enhancing the efficacy of acid recovery. Notably, the optimal CPIM-BPY-5h exhibits superior performance ( U H +  = 51.07 × 10 −3  m h −1 , S H + / F e 2 +  = 52.16) in the HCl/FeCl 2 system at 25 °C, outperforming the commercial DF-120 AEM by approximately 6.0-fold in U H + and over 2.8-fold in S H + / F e 2 + , while demonstrating comparable performance to our previous porous AEMs derived from ultrafiltration membranes, which, based on current literature, achieve unprecedented U H + values. However, the CPIM-BPY-5h distinguishes itself with significantly enhanced mechanical integrity. This work highlights the effectiveness of our strategy in producing membranes with excellent ion transport capabilities, mechanical strength, and acid and solvent stability, making them promising candidates for high-performance acid recovery applications.