Solvothermal synthesis and enhanced electrochromic properties of coal-based reduced graphene oxide and covalent organic framework electrochromic composite films containing triphenylamine unit

Two-dimension covalent frameworks (2D COFs) with reversible redox units show the potential in the field of photo-electronic functional materials because of their rich electron transport path and reversible redox characteristic. However, the pure organic conjugated system of COF results in poor electrical conductivity and weak cyclic performance. In this work, tris (4-aminophenyl) amine and 4,4-biphenyldiformaldehyde (TABP) COF electrochromic film with triphenylamine (TPA) active unit was synthesized by a solvothermal method in Teflon-lined reactor. And then the TABP-COF/coal-based reduced graphene oxide (C-rGO) film was prepared by the one pot method. C-rGO provides the growth substrate and electron transport path for COF. Taixi anthracite with a high degree of graphitization also contributes to the preparation of GO. The electrochemical and electrochromic properties of TABP-COF and TABP-COF/C-rGO were studied and they could be switched reversibly from yellow and brown. Relative to TABP-COF, the impedance and response time of composite decrease and the contrast of composite increases. Moreover, TABP-COF/C-rGO exhibits the excellent stability, which can remain 80.1 % initial contrast after 5000 s cycle.