Redox-Active Triphenylamine-Triazine Covalent Organic Framework: A High Surface Area Microporous Material for Electrochromism and Electrofluorochromism.

Porous covalent organic frameworks (COFs) offer significant advantages in electrochromic (EC) applications due to their high surface area and porosity, which facilitate faradaic redox-mediated diffusion-controlled processes. However, COFs remain underexplored as EC materials due to challenges such as limited solubility and poor film-forming ability. In this study, we synthesized a redox-active triphenylamine-containing COF (TPA-TCIF) on ITO glass via a solvothermal method tailored for electrochromism and electrofluorochromism. The COF, formed through the condensation of tris(4-formyl phenyl)amine and 2,4,6-tris-(4-aminophenyl)-1,3,5-triazine, features a high surface area of 1136.8 m/g and a pore diameter of 1.18 nm. This structure promotes efficient ion transport, reducing switching times and enhancing coloration efficiency (CE). Reversible redox reactions induce a color change from yellow to red, with an optical contrast (ΔT) of 37 % and a CE of 47.7 cm/C. The film exhibited stable electrofluorochromic (EFC) behavior, switching from yellow emissive to dark black upon voltage application, with stability over 40 cycles. A quasi-solid-state electrochromic device (ECD) based on TPA-TCIF demonstrated reversible color transitions, showcasing its potential for future display technologies and highlighting the promise of COFs in advanced EC applications.