Solvothermal synthesis of donor-acceptor covalent organic framework/coal-based polyaniline composites for three-state electrochromic materials

Abstract

Conjugated covalent organic frameworks (COFs) with redox activity can be designed for photoelectric materials application. In this paper, COF based electrochromic films were synthesized by solvothermal method in a Teflon-lined reactor, with thieno [3,2-b]thiophene-2,5-dicarbaldehyde (TTDA) as electron donor unit (D) and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TTA) as electron acceptor unit (A) (COF TT ). Coal-based polyaniline (CPANI) was used as COF TT growth substrate and conductive enhancing agent to improve the photoelectric performance of COF TT . The addition of CPANI results in the morphology transformation of COF TT from nanosheet to nanofiber. Meanwhile, the impedance of COF TT is reduced and the optical contrast is improved. The color of COF TT -CPANI-1 can vary from yellow to dark orange and brown under a voltage window of −3 V–2.2 V. Stability tests show that the contrast retention rate of the electrochromic device is 90.6% after 1600 s switching. Considering the rich selectivity of COF construction units and the designability of topological structure, the development of COF-based electrochromic materials with rich colors and excellent properties has a broad prospect. • A COF electrochromic film was prepared by solvothermal method. • The morphology and photoelectrical properties of COF films was changed by the addition of coal-based polyaniline. • Due to the donor-acceptor properties of the synthesis unit, the COF film presents a three-state electrochromic behavior.