A Bipolar Carbonaceous Framework for Highly Electro-Responsive Smart Materials

Abstract Various framework materials offer potential platforms for developing next-generation electro-responsive functional and smart materials because they are electro-active or polarizable by either ions in channels or electrons in frameworks. However, the present framework materials still face challenges in achieving high electro-response while maintaining low charge leakage or electrode polarization. In this study, we developed a kind of bipolar carbonaceous framework (CF) materials codoped with pyridinic nitrogen and graphitic nitrogen, which can simultaneously provide local electrons and holes, via an ionothermal polymerization of task-specific ionic liquid at target temperature. The structure of CF was characterized by thermogravimetric analysis, Fourier transform infrared spectra, solid-state nuclear magnetic resonance spectra, wide-angle X-ray scattering spectra, and X-ray photoelectron spectra, and the bipolar charge characteristic was analyzed by Mott–Schottky curves and photocurrent measurements. Dielectric spectra of the CF particles in suspensions were measured and showed enhanced interfacial polarization but very weak electrode polarization and leakage conduction due to the coupled movement of electrons and holes. Consequently, the bipolar CF suspensions show significantly higher electro-responsive electrorheological effect (τs = 12 kPa@3 kV/mm) and lower current density (j = 46 μA/cm2@3 kV/mm) compared to single electron-dominated, single ion-dominated, and even mixed ionic-electronic systems. So, this bipolar CF provides a preferred platform for the design of high-performance carbonaceous-based electro-responsive functional and smart materials.