Redox-Active Ni(II) Nodes Induced Electrochromism in a Two-Dimensional Conductive Metal-Organic Framework

Metal-organic frameworks (MOFs) are highly desired for electrochromic (EC) applications because of their designable porous structures for fast ionic transport. However, the intrinsic low electronic conductivity of traditional MOF-based EC materials leads to a slow switching speed, poor coloration efficiency, and unfavorable cyclability. Conductive MOFs, with a tunable porous crystal structure and highly improved electronic conductivity, are proposed as promising candidates to achieve synchronous high-speed transport of electrons and ions in the EC process. Here we demonstrate fast and high-coloration-efficiency EC electrodes based on interfacially assembled conductive MOF Ni-3(HITP)(2) films. The reversible EC behavior of Ni-3(HITP)(2) is systematically explored and elaborated as the redox of Ni nodes in the crystal. Finally, we demonstrate MOFs-based devices that could potentially be used in fields such as digital displays and optical modulation.