Anion exchange membrane incorporating polymers of intrinsic microporosity for large organic anions

Abstract

To meet a growing demand for the applications of electro-membrane technologies in the fields related to organic acid, this work attempts to incorporate polymers of intrinsic microporosity (PIM) with rigid and twisted structure into the preparation of anion exchange membrane (AEM) and investigates the possible effects of PIM addition on the transport behaviors of bulky organic anions therein. Firstly, molecular dynamics simulations are conducted to optimize the blend ratio between the modified PIM and chloromethylated Polysulfone. Furthermore, performances of as-prepared AEMs with different blend ratios are evaluated in some typical organic salt systems, including sodium lactate, sodium gluconate, and sodium citrate. Results demonstrate that water uptake increases and electrical resistance decreases significantly with increasing PIM loading despite the moderate reductions in ion exchange capacities. For example, a reduction of >50 % in electrical resistance when the PIM fraction increases up to 20 %. Small angle X-ray scattering reveals that these changes appear to be the result of micro-phase separation and increase of internal free volume. Additionally, electrometathesis-based organic acid conversion experiments confirm that the blend AEMs indeed contribute to reduce process energy consumption, for instance, a reduction of up to 23.29 % for the gluconic acid conversion. Although the addition of PIM results in a loss of membrane permselectivity to some extent, the corresponding current efficiency is still acceptable. Incorporation of Polymers of Intrinsic Microporosity is worth exploring for the preparation of Bulky Organic Anions-oriented AEM.