Coordination‐Induced Structural Rigidity for Achieving Ultralong‐Lived Aqueous Room Temperature Phosphorescence

Abstract Designing ultralong‐lived aqueous room temperature phosphorescence (RTP) materials has become an actively pursued but challenging research area. Herein, a coordination‐induced structural rigidity (CISR) strategy is proposed to achieve ultralong RTP lifetime in magnesium/pyromellitic acid phosphorescent materials (Mg/PMA‐PMs) with abundant Mg²⁺ ions sites and hydrophilic groups in aqueous solution. Compared to their dry state (448.77 ms), the lifetime of Mg/PMA‐PMs significantly increases to 1026.17 ms with the addition of a small amount of water (50 wt%). Even in a fully non‐deoxygenated aqueous environment (above 200 wt% water), where Mg/PMA‐PMs disintegrate to form a nanosuspension, they still exhibit an ultralong aqueous RTP lifetime of ≈800 ms. The water‐enhanced RTP properties are attributed to water molecules coordinating with Mg²⁺ ions and acting as bridging agents to bind with hydrophilic groups through hydrogen bonding. This interaction rigidifies functional groups and inhibits their motions, leading to a substantial reduction in nonradiative decay. Furthermore, the CISR mechanism effectively explains the RTP enhancement effect of water on inorganic salt phosphorescent systems. This work not only provides a new approach for constructing efficient aqueous RTP materials, but also develops a powerful tool for visual anion recognition.