Leveraging Thermally Activated Delayed Fluorescence and Dual Room-Temperature Phosphorescence for Tri-Mode Color-Tunable Afterglow in Zinc Halides

Color-tunable afterglow materials have attracted extensive attention due to their unique optical properties. However, most afterglow materials often face limitations such as monochromatic emission and short lifetimes, which restrict their practical application. Herein, we employed 1-(pyrid-4-yl)piperazine (PyPi) as organic template and chromophore and prepared two isomorphic zero-dimensional (0D) afterglow metal-organic halides (MOHs), (H₂-PyPi)[ZnX₄] (X = Cl^-, Br^-). Interestingly, both MOHs exhibit trimode (excitation wavelength, temperature, and time evolution) color-tunable afterglow by leveraging thermally activated delayed fluorescence and dual room-temperature phosphorescence derived from the coemissions of pristine H₂-PyPi molecules and halogen-affected H₂-PyPi molecules. Two MOHs were successfully applied to a high-security anticounterfeiting and encryption system, achieving dynamic "firework" patterns and "0 → 7" or logic gate information encryption. That is, the introduction of suitable halogen ions into afterglow materials could be a facile way to construct color-tunable afterglow MOHs by adjusting excited state energy levels. This work provides a new strategy for developing color-tunable photoluminescent materials and expands their application potential in the fields of optical anticounterfeiting and information encryption.