Mixed Ionic-Electronic Covalent Organic Frameworks as a Platform for High-Performance Electro-Responsive Smart Materials

Ionic covalent organic framework (iCOF) materials are providing a potential platform to develop next-generation electro-responsive smart materials because of ion movement-induced interfacial polarization. However, it is challenging to achieve strong interfacial polarization while reducing electrode polarization due to the nature of pure ions as charge carriers in iCOF. In this article, we developed a mixed ionic-electronic covalent organic framework (ieCOF), which can overcome this challenge. This ieCOF was prepared by thermal cracking of task-specific ionic liquids. It shows that ieCOF is composed of a positively charged slight-carbonized framework attracted with fluoric counteranions. Through changing the heating target temperature, ieCOF with different ion contents and different carbonized level frameworks can be obtained. We find that compared with the ion-dominated system, the mixed ionic-electronic ieCOF can achieve a stronger interfacial polarization but a weaker electrode polarization. Consequently, the ieCOF has a higher electro-responsive electrorheological (ER) effect but lower leaking current density. In particular, increasing the temperature can promote the interfacial polarization intensity, resulting in a higher ER effect. The present result shows that ieCOF can provide a platform to design and develop high-performance electro-responsive smart materials.