Application of Ionic Hydrogen-Bonded Organic Framework Materials in Hybrid Proton Exchange Membranes

Abstract

Excellent and inexpensive materials with proton conductivity have far-reaching significance for the development of clean energy. In this paper, three ionic hydrogen-bonded organic frameworks (iHOFs) were synthesized using naphthalenedisulfonate derivatives with substituents at different positions and 1,1′-diamino-4,4′-bipyridylium. The hydrogen bond networks were formed by sulfonic acid groups and amino groups, while the addition of functional groups such as hydroxyl or amino groups can also enrich the hydrogen bonds, which also makes such iHOFs have high conductivity, in which iHOF-7 afforded the highest proton conductivity of 4.5 × 10–3 S·cm–1 at 100 °C, 85% relative humidity (RH). It is difficult for the crystalline materials to form a membrane, so we prepared the hybrid membranes of iHOF-7 using sulfonated poly (ether ether ketone) (SPEEK) or chitosan (CS) as the supporting polymeric matrix. At 85% RH and 100 °C, the highest proton conductivity of the 15%-iHOF-7/SPEEK composite membrane can reach 5.1 × 10–3 S·cm–1, and at 98% RH and 100 °C, the highest proton conductivity of 15%-iHOF-7/CS can reach to 5.7 × 10–3 S·cm–1.