Boosting dynamic fluorescent materials using SP@Tb-MOFs through the alkyl functionalization of pores and applications in time-dependent information encryption

Dynamic fluorescent materials have received widespread attention in the fields of data storage and antic-ounterfeiting technology. Here, we present a new approach to achieving dynamic fluorescent materials by introducing spir-opyran (SP) molecules into alkyl-chain-modified lanthanide metal-organic frameworks (Ln-MOFs). Alkylated ligands can serve as both bridging ligands and structural directors to regulate the morphology of Tb-MOFs. By controlling the length of the alkyl chain, the morphology of Tb-MOFs was adjusted, thus further regulating the photochromic behaviors of the composite system. When the alkyl chain is short, the composite system emits yellow or even green emissions. Only SP@Tb-MOF-10C shows the green emission of Tb³⁺ at 545 nm and the red emission of SP at 650 nm. Under continuous irradiation of 365 nm ultraviolet (UV) light, SP molecules underwent a photoisomerization process to the open-ring form, leading to a significant fluorescence resonance energy transfer between Tb-MOF and its isomer merocyanine (MC). These composites exhibit dynamic fluorescence behavior and can be fully restored to their initial states when exposed to white light. In addition, a composite film was prepared by doping with polydimethylsiloxane (PDMS). Its applications in anticounterfeiting labels and time-resolved dynamic encryption were demonstrated.