Electrochromic thin films of Zn-based MOF-74 nanocrystals facilely grown on flexible conducting substrates at room temperature

Abstract

Electrochromic materials can reversibly switch color subject to the application of an externally applied electrical potential, making them useful for advanced applications such as smart windows, sensors, and electrochromic displays. To date, the development of electrochromic metal-organic frameworks (MOFs) is hampered by their insulating framework and nonredox active moieties. Herein, we demonstrate the use of the Guest@MOF concept to engineer electrochromic thin films, termed “DHTP@Zn-MOF-74,” grown on a flexible PET polymer substrate coated with a transparent indium tin oxide conductor. This electrochromic film reversibly switches between the (transparent) colorless ⇄ magenta states, by employing a relatively low cyclic voltage of 0 V and −2.5 V, and is tested under a variable scan rate ranging from 50 mV/s up to 1 V/s. This study could open the door to the discovery of new Guest@MOF electrochromic systems with tunable properties for energy applications.