Redox Activities of Metal–Organic Frameworks Incorporating Trinuclear Mn/Co Clusters and Bis(triarylamine) Linkers

Metal–organic frameworks (MOFs) featuring multiple redox-active centers have attracted significant attention due to their unique electron transfer properties in optical and electrical functional fields. In this study, tetrakis(1,1’-biphenyl-4-carboxylic acid)-1,4-benzidine (H4BTPPA) was used as an organic ligand to construct two isomorphic MOFs, specifically Mn3–BTPPA and Co3–BTPPA, through trinuclear Mn3 and Co3 inorganic nodes. Both Mn3–BTPPA and Co3–BTPPA demonstrated excellent crystallinity and good chemical and thermal stability, as well as reversible redox activity. Notably, electrochemical tests revealed that both MOFs exhibit two reversible and readily accessible oxidation states, with an approximate 0.1 V difference in the first redox potentials between the two MOFs. Based on the characteristic two-electron reversible redox-active BTPPA building block, Mn3–BTPPA and Co3–BTPPA were employed to construct electrochromic devices, which demonstrated three color transitions from light to dark within a potential range of 0.6–1.4 V. This work clearly demonstrates that the redox potential of MOFs can be modulated by the coordination effect of different metal ions, highlighting the potential applications of these two-electron reversible redox-active MOFs in various functional areas.