Rapid and selective acid recovery enabled by structurally engineered, high-surface-area PIM-1 anion exchange membranes

To advance industrial acid recovery via diffusion dialysis, the crucial step is to engineer anion exchange membranes (AEMs) with superior acid permeability and selectivity. Herein, a PIM-1-based AEM was fabricated via liquid bromine-induced bromination followed by a non-crosslinking alkylation with 1-methylimidazole, which preserves the rigid polymer backbone and intrinsic microporosity. The optimized, mechanically robust membrane exhibited a specific surface area of 549 ± 18 m 2  g −1 , providing abundant free volume for rapid proton transport, and a pore size distribution precisely centered between 0.40 and 0.75 nm, enabling selective acid recovery via size sieving in a typical HCl/FeCl 2 wastewater system. This membrane achieved a proton dialysis coefficient of 59.4 ± 4.3 × 10 −3  m h −1 and a selectivity of 74.4 ± 2.7 over Fe 2+ , outperforming the commercial DF-120 AEM by sevenfold and fourfold, respectively. This work provides a scalable, non-crosslinking functionalization route to fabricate mechanically robust AEMs from PIMs, leveraging their preserved microporosity for efficient and selective acid recovery.