Electrochromic two dimensional covalent organic framework with a reversible dark to transparent switch
Electrochromic (EC) materials with a dark to transmissive switch have great applications in optical communications, infrared wavelength detectors for spacecraft, and infrared camouflage coatings. However, such electroactive materials with high stability and cyclability are rare. Considering the advantages of the donor acceptor approach (wide range tuneable band position) and porous two dimensional (2D) covalent organic framework (COF, well ordered crystalline framework with stable structure and high surface area) in this work we constructed an extended delocalised p electron layered dark purple EC COF 1 by reacting the donor N,N,N',N' tetrakis(p aminophenyl) p benzenediamine (TPBD) with the acceptor 2,1,3 benzothiadiazole 4,7 dicarboxaldehyde (BTDD) A sandwiched device made of EC COF 1 exhibits the two band bleaching (370 nm and 574 nm) in the visible region and becomes transparent under the applied potential with an induced absorption centring at 1400 nm. This discovery of a stable dark to transmissive switch in COF might open another door for their application in many EC devices for various purposes.
Nature communications