A Sodium Metal−Organic Framework with Deep Blue Room‐Temperature Phosphorescence

It is a great challenge to manufacture room‐temperature blue long afterglow phosphorescent materials adapted to environmental conditions. Herein, an Na‐based metal−organic framework (MOF) was constructed using Na+ and 1H‐1,2,4‐triazole‐3,5‐dicarboxylic acid, which exhibits long‐lived of 378.9 ms, deep blue and room‐temperature phosphorescence, meanwhile possesses the visible blue afterglow for 3~6 seconds after removing excitation light source. The three‐dimensional coordination bonds network provided by Na‐based MOF protects the organic ligands intrinsic hydrogen bond network, resulting in the phosphor lifetime and residual color remaining unchanged in different gas atmospheres. Furthermore, first‐principles time‐dependent density functional theory reveals that the rigid Na‐based MOF structure can limit the rotation and vibration of the room‐temperature phosphorescent organic ligands. This limitation results in the suppression of non‐radiative decay for both singlet and triplet excitons, promotes intersystem crossing, and increases the rate of radiative decay, ultimately achieving long‐lived room‐temperature phosphorescence.