Highly Cationized and Porous Hyper-cross-linked Polymer Nanospheres for Composite Anion Exchange Membranes

Hyper-cross-linked polymer (HCP), a category of porous organic materials (POMs), is exploited as an anion conducting membrane via a highly cationized and porous quaternized ammonium triptycene-based HCP in the form of <100 nm nanospheres (QTP-HCP-NS) for the first time. The material possesses a high ion density of 3.65 mmol g–1 as well as a high Brunauer–Emmett–Teller (BET) surface area of 706 m2 g–1. Anion exchange membranes (AEMs) are prepared by mixing different loadings of QTP-HCP-NS with quaternized poly(phenylene oxide) (QPPO) and compared with a compressed QTP-HCP pellet. Owing to the high ion density and high water sorption, which results in abundant ion conduction channels in QTP-HCP, the ion conductivity of the composite AEMs is enhanced by 79.5% compared with the unfilled QPPO membrane and by 677% compared with a compressed QTP-HCP pellet. In addition, lower dimensional swelling and higher tensile strength are achieved for the composite AEMs. Aggregation and the resulting interfacial defects of QTP-HCP-NS are found in the composite AEM at a high loading and in the comparative compressed pellet, causing a significant reduction in ion conduction and mechanical properties.