Interfacial modification strategy for enhanced electrochromic performance of the Cu-based metal-organic framework

Metal-organic frameworks (MOFs) exhibit great potential in electrochromic applications owing to their tunable pore structure and abundant redox active sites. Among them, the Cu-based MOF—Cu-TCA (H 3 TCA = 4,4′,4′′-nitrilotribenzoic acid) stands out as an ideal electrochromic material due to its dual redox activity. However, challenges such as particle agglomeration and weak interfacial adhesion between Cu-TCA and substrates hinder its electrochromic performance. Here, we propose a novel interfacial modification strategy combining oxygen plasma (OP) with self-assembled molecules (SAMs) to modify indium-doped tin oxide (ITO) -coated glass substrates. The OP@SAMs layer enhances the adhesion between Cu-TCA and substrates via coordination bonds, and facilitates the formation of uniform Cu-TCA crystals with large ion transport channel size (8.4 Å), large pore volume (0.136 cm 3 ·g −1 ), and high porosity (0.209), to improve the electrochemical cycling durability and accelerate ion transfer, thus achieving superior electrochromic performance. Results demonstrate that the Cu-TCA thin film grown on the OP@SAMs-modified ITO-coated glass substrate exhibits large transmittance modulation (~ 56 %), short coloration/bleaching time (3.7 s/1.0 s), high coloration efficiency (287.2 cm 2 ·C −1 ), and superior cycling stability (1000 cycles). The corresponding Cu-TCA electrochromic device also exhibits outstanding electrochromic performance. This study provides a novel strategy for developing high-performance MOFs-based electrochromic materials and offers valuable references into interfacial engineering for the synthesis of MOFs-based thin films.