Solvothermal synthesis and enhanced electrochromic properties of covalent organic framework/functionalized carbon nanotubes composites electrochromic materials with anthraquinonoid active unit

Two-dimension covalent organic frameworks (2D COFs) are porous materials with the interlayer π-π interaction and excellent optoelectronic properties. Their adjustable porous structure and designable molecular structure endow them unlimited possibilities in the field of optoelectronic materials and other functional materials. In this paper, 2D COF electrochromic films were prepared by solvothermal synthesis method with different amounts of functionalized carbon nanotubes (FCNT) loading to improve their conductivity. The morphology characterization of COF DAAQ-TFP reveals its intertwined nanofiber structure. The electrochromic performance of COF DAAQ-TFP film shows that the color of COF DAAQ-TFP and FCNT-COF DAAQ-TFP have a reversible transformation from orange to dark brown during the redox process. When the loading amount of FCNT is 1%, FCNT-COF DAAQ-TFP exhibits best electrochromic properties, which has a contrast of 0.358 and coloring time of 5.7 s. Relative to COFs, FCNT-COF has enhanced contrast and stability, which is a potential electrochromic material in many fields such as smart window and smartphone back case. • A COF electrochromic film with anthraquinonoid active unit was prepared by solvothermal method. • The COF was combined with FCNTs by covalent bond. • The addition of FCNT improves the conductivity and electrochromic performance of the composite.