Engineering Dopant‑Modulated Fluorescence and Excitation‑Directed Afterglow in 2D Organic‐Inorganic Metal Halides for Multilevel Dynamic Encryption

Herein, we report a novel class of 2D organic‐inorganic metal halides, An 2 CdCl 4 , based on anilinium chloride (An) and its Sb 3+ ‐doped derivatives An 2 CdCl 4 :x%Sb. This system overcomes limitations of existing long‐persistent luminescent materials in color tunability and dynamic responsiveness. Through controlled Sb 3+ doping, the material exhibits precise modulation of steady‐state photoluminescence across blue, white, and yellow emission. Notably, it demonstrates remarkable room‐temperature phosphorescence (RTP) and, for the first time in such materials, excitation‐wavelength‐dependent afterglow with continuous color gradation from blue to green and yellow. The corner‐sharing [CdCl 6 ] 4− octahedral network, with halogen aggregation effects, induces multiple phosphorescent centers. Sb 3+ doping enhances octahedral distortion and lattice rigidity and promotes energy transfer from triplet excitons of An + to self‐trapped excitons (STEs) at [SbCl 6 ] 3− sites. This synergy enables multimodal (fluorescence/phosphorescence) and multicolor responsive luminescence. Based on these photophysical properties, an advanced information encryption platform integrating wavelength‐responsive patterns, time‐resolved color codes, and magic cubes was constructed, demonstrating its potential for dynamic information encryption.