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.