Ultra-stable Ionic-Liquid-based Electrochromism Enabled by Metal-Organic Frameworks

Room temperature ionic liquid (RTIL) electrolytes are excellent candidates for highly stable electrochromic (EC) devices because of their wide electrochemical windows and good environmental stability. However, the small crystal spacings and molecular gaps of conventional EC materials limit the ion-diffusion rate of RTILs’ large cations. The multiple insertions/extractions of large cations can destroy the structure of the conventional EC materials, leading to structural collapse and poor EC performance. Here, we demonstrate that metal-organic frameworks (MOFs) with large intrinsic pores in crystals are promising materials for stable and high-performance RTIL-based EC systems. The MOFs’ large intrinsic hexagonal channels provide suitable ion-transport channels for RTILs, leading to ideal electrochemical stability. We further demonstrate a patterned large-area MOF/RTIL-based EC device, suggesting the promise in future digital displays.