Direct fabrication of electrochromic Ni-MOF 74 film on ITO with high-stable performance

Metal–organic framework (MOF) is a promising electrochromic material due to its high specific surface area and tunable pore size, which can benefit the fast transportation of ion/charge. Here, a simple solvothermal deposition method for fabrication of Ni-MOF 74 electrochromic films on ITO is developed. It is found that the reaction temperature has played an important role in the morphology and electrochromic performance of as-prepared Ni-MOF 74 film. The film prepared at the optimized temperature exhibits the best electrochromic performance with a rapid switching speed (the coloration/bleaching time = 24.5/23.5 s). In addition, the optimized film displays a high optical contrast of 44.4% at 550 nm and can be stably switched for 650 cycles with < 21.5% contrast attenuation. The electrochromism of Ni-MOF 74 can be attributed to the oxidized and reduced states of 2,5-dihydroxyterephthalic acid ligands. This simple method can be broaden to fabricate other metal-based MOF films for electrochromic applications.