Abstract Electrochromic metal-organic frameworks (MOFs) combine advantages from both inorganic/organic electrochromic materials by enabling stable structures/performances as well as tunable functionalities. Their current design and synthesis, however, are inherently complicated as often involving amends to the chromogenic components and/or MOF structures. Inspired by the reticular chemistry, we herein demonstrate a multi-directional ‘color palette’ based on the colorful electrochromic behaviors across a total of forty zirconium-based MOFs via systematically combining diverse naphthalene diimide (NDI) based primary-linkers (R-groups) and auxiliary-linkers (X-groups), namely the NKM-908-R/NKM-906-R series (csq/scu topology) and their corresponding NKM-908-R-TPDC-X/NKM-906-R-TPDC-X derivatives. Novelly, a broad color gamut over these robust MOF thin films was showcased via systematical crystal engineering and was thoroughly investigated. These include enhancing the primary set of ‘colors’ from altering peripheral R-groups without redesigning the NDI core, introducing different X-groups as the secondary sets of ‘colors’, and topology adjustments to incorporate more X-linkers for intensification of the latter. Together, such designable color mixing/changing sequences successfully mimicked the use of routine color palette at a molecular-level precision. Not only holds great potential in further extension, this work also provides unique insights in developing next-generation electrochromic devices.
Li et al. (Fri,) studied this question.