Blue-LED Photocatalytic Synthesis of Large-Area Benzobisazole-Based 2D Zwitterionic Polymer Membranes for Durable Proton Exchange

The development of sustainable energy technologies requires green synthetic routes to produce robust proton exchange membranes (PEMs). We report the blue-LED-driven photocatalytic synthesis of large-area, two-dimensional imine-linked benzobisazole-based polymer membranes, followed by post-addition of zwitterions (ZA@IO-2DP, ZA@IS-2DP, ZA@II-2DP) that exhibit excellent mechanical properties and are durable proton conductors. The membranes exhibit proton conductivities of 6.11 × 10⁻⁴, 1.05 × 10⁻³, and 2.04 × 10⁻³ S/cm at 80 °C (98% RH) for ZA@IO-2DP, ZA@IS-2DP, and ZA@II-2DP, respectively, showing an increasing trend governed by the intrinsic proton affinity caused by the structural motif of the sulfonated benzobisazole-based moieties in a humid environment, where water-mediated transport complements the intrinsic benzobisazole-based pathways via the Grotthuss mechanism. The outstanding performance of ZA@II-2DP stems from its dual donor-acceptor nitrogen sites, forming an effective interface that facilitates hydrated proton-conduction pathways. Overall, this green, scalable synthesis pathway yields 2D polymer membranes with tunable proton-conducting interfaces, paving the way for next-generation sustainable energy devices.