Visible‐Light‐Activated Multi‐Color Room Temperature Phosphorescence Under Extreme Aqueous Environment and High Temperature via Supramolecular Assembly

ABSTRACT Organic room‐temperature phosphorescence (RTP) materials have attracted extensive attention for their promising applications. However, they frequently suffer from severe deactivation under extreme conditions (aqueous environment and high temperature) and rely exclusively on ultraviolet (UV) excitation, which greatly limits their reliability and utility. Herein, we present an efficient supramolecular assembly strategy to achieve visible light‐activated organic phosphorescence under extreme environments, including various aqueous media (acidic, alkaline, oxidizing, or reducing solutions) and high temperature. AC@AMD is constructed via hydrogen bonds and covalent interactions between aromatic acid (AC) and ammelide (AMD), providing a rigid microenvironment. This structure effectively reduces the singlet–triplet energy gap (Δ E _ST ) and enhances spin–orbit coupling (SOC), endowing AC@AMD with efficient RTP: phosphorescence quantum yield ( Φ _P ) up to 34.31% and lifetime ( τ _P ) of 1094.99 ms. Moreover, the formation of hydrogen‐bonding networks further enhanced the rigidity of AC@AMD, making them with the excellent phosphorescence features in aqueous solutions. More importantly, the compact lamellar structure and the strong stability of the matrix skeleton structure of AC@AMD due to the presence of abundant N─C═N and N─C═O bonds endow them with excellent tolerance to various extreme aqueous solutions and high temperature. In view of the above‐mentioned advantages, information encryption, anti‐counterfeiting labeling, and bioimaging applications are demonstrated.