Scaffolding\nand Heavy-Atom Effects of Metal Chains\nEnhanced Tunable Long Persistent Luminescence in Metal–Organic\nFrameworks

Metal–organic frameworks (MOFs) with long persistent\nluminescence\n(LPL) have attracted extensive research attention due to their potential\napplications in information encryption, anticounterfeiting technology,\nand security logic. The strategic combinations of organic phosphor\nlinkers and metal ions lead to tremendous frameworks, which could\nunveil many undiscovered properties of organics. Here, the synthesis\nand characterization of a three-dimensional MOF (Cd-MOF) is reported,\nwhich demonstrates enhanced blue photoluminescence and a phosphorescent\nlifetime of 124 ms as compared to the pristine linker (H<sub>2</sub>L) under ambient conditions due to the scaffolding and heavy-atom\neffects of metal chains in the framework. Notably, the Cd-MOF exhibits\nintriguing excitation-, time-, and temperature-dependent LPL, with\na duration of 3 s at room temperature and the ability to shift from\nblue to green to yellow at lower temperatures. Optical characterizations\nand theoretical calculations reveal that H<sub>2</sub>L molecules\nare responsible for the emissions in the Cd-MOF, while LPL properties\nof molecular phosphors can be significantly enhanced and regulated\nthrough coordination interactions and heavy-atom effect of the metal\nchains. This work highlights the potential of such materials as promising\ncandidates for multiple anticounterfeiting, displaying, and encryption\napplications.