Crystal‐Armoured Aromatic Anhydride Molecules Enable Time‐Dependent Organic Ambient‐to‐Harsh Phosphorescence

ABSTRACT Organic time‐dependent phosphorescence color (TDPC) materials, which exhibit dynamic afterglow color evolution, represent a cutting‐edge advancement in security technologies. However, constructing TDPC materials remains highly challenging due to the difficulty in precisely modulating multiple emissive species with distinct yet comparable lifetimes, while their inadequate experimental tolerance further limits practical applications. Herein, we propose an effective crystal‐armoured strategy that confers exceptional robustness to TDPC materials by embedding aromatic anhydride‐derived within a biuret (Biu) crystalline matrix. The rigid confinement of the crystalline Biu framework synergizes with the formation of interfacial covalent bonds to immensely suppress nonradiative transitions, thereby stabilizing triplet excitons. Consequently, the resulting AA@Biu composites exhibit tunable full‐color TDPC, originating from the differential decay rates of emission centers corresponding to the dispersed and aggregated states of the aromatic anhydride. Moreover, these Biu‐armoured aromatic anhydride composites exhibit exceptional tolerance to harsh conditions, maintaining intense phosphorescence and evident TDPC behavior even after prolonged water immersion (30 days), exposure to strong acids/bases, and at high temperatures up to 473 K. Leveraging these advantages, we demonstrate the great potential of these robust materials in multi‐level dynamic anti‐counterfeiting and time‐gated information encryption applications, significantly broadening the operational scope of organic phosphorescent materials in real‐world scenarios.