Oriented Surface‐Anchored Metal–Organic Frameworks (SurMOFs) as Electrochromic Thin Films

Abstract Novel electrochromic hybrid thin films are synthesized following a liquid‐phase epitaxy in a layer‐by‐layer fashion, yielding highly oriented surface‐anchored metal–organic frameworks (SurMOFs). The initial orange color of this Zn 2 (PDICl 4) 2 crystalline thin films is reversibly switched by electrochemical reduction. In a lithium‐based electrolyte, a dark blue color is obtained in few seconds with a color efficiency of 104. 8 cm 2 C −1 (λ = 645 nm). Interestingly, the color of the reduced state is easily modulated by changing the electrolyte composition. Clearly, two different mechanisms are implicated and the reduced species responsible of the color are identified. Taking advantage of this unusual property, electrochromic devices with a novel configuration are designed leading to an original prototype capable of reversibly switching from a single initial orange color to two different colors simultaneously, namely dark blue and cyan.