Ultrathin Free‐Standing Porous Aromatic Framework Membranes for Efficient Anion Transport

Porous aromatic frameworks (PAFs) show promising potential in anionic conduction due to their high stability and customizable functionality. However, the insolubility of most PAFs presents a significant challenge in their processing into membranes and subsequent applications. In this study, continuous PAF membranes with adjustable thickness were successfully created using liquid‐solid interfacial polymerization. The rigid backbone and the stable C−C coupling endow PAF membrane with superior chemical and dimensional stabilities over most conventional polymer membranes. Different quaternary ammonium functionalities were anchored to the backbone through flexible alkyl chains with tunable length. The optimal PAF membrane exhibited an OH− conductivity of 356.6 mS ⋅ cm−1 at 80 °C and 98 % relative humidity. Additionally, the PAF membrane exhibited outstanding alkaline stability, retaining 95 % of its OH− conductivity after 1000 hours in 1 M NaOH. To the best of our knowledge, this is the first application of PAF materials in anion exchange membranes, achieving the highest OH− conductivity and exceptional chemical/dimensional stability. This work provides the possibility for the potential of PAF materials in anionic conductive membranes. A series of ultrathin free‐standing porous aromatic framework (PAF) membranes were prepared by liquid‐solid interfacial polymerization, and applied in the anion conduction for the first time, with excellent performance in hydroxide conductivity and stability due to the rational presence of transporting sites and rigid structure of PAF.