Scaffolding and Heavy-Atom Effects of Metal Chains Enhanced Tunable Long Persistent Luminescence in Metal–Organic Frameworks

Metal-organic frameworks (MOFs) with long persistent luminescence (LPL) have attracted extensive research attention due to their potential applications in information encryption, anticounterfeiting technology, and security logic. The strategic combinations of organic phosphor linkers and metal ions lead to tremendous frameworks, which could unveil many undiscovered properties of organics. Here, the synthesis and characterization of a three-dimensional MOF (Cd-MOF) is reported, which demonstrates enhanced blue photoluminescence and a phosphorescent lifetime of 124 ms as compared to the pristine linker (H₂L) under ambient conditions due to the scaffolding and heavy-atom effects of metal chains in the framework. Notably, the Cd-MOF exhibits intriguing excitation-, time-, and temperature-dependent LPL, with a duration of 3 s at room temperature and the ability to shift from blue to green to yellow at lower temperatures. Optical characterizations and theoretical calculations reveal that H₂L molecules are responsible for the emissions in the Cd-MOF, while LPL properties of molecular phosphors can be significantly enhanced and regulated through coordination interactions and heavy-atom effect of the metal chains. This work highlights the potential of such materials as promising candidates for multiple anticounterfeiting, displaying, and encryption applications.