Circular Modulation Pathway of the Afterglow Color in Metal‐Organic Coordination Polymer

Abstract Long‐lived organic luminescence materials with color‐tunable afterglow have attracted considerable attention due to potential applications in display and information encryption. Nevertheless, the majority of these materials currently have limited capability for regulating the afterglow color in only one direction. Here, a metal‐organic coordination polymer (Zn‐PTZ‐O) is presented that demonstrates the ability to modulate its afterglow color in a circular modulation pathway. As the temperature increases from 77 to 400 K, the afterglow color red‐shifts from blue to green, and then blue‐shifts back to blue, achieving circular modulation. This outstanding phenomenon is attributed to the concurrence of long‐lived thermally activated delayed fluorescence and phosphorescence emission of Zn‐PTZ‐O. Furthermore, the afterglow color of Zn‐PTZ‐O also has forward and reverse excitation wavelength dependence at 77 K and room temperature, respectively. As the excitation wavelength increases from 340 to 460 nm at 77 K, the afterglow color of Zn‐PTZ‐O red‐shifts from blue to yellow. While as the excitation wavelength increases from 375 to 410 nm at room temperature, the afterglow color blue‐shifts from yellowish‐green to blue, almost forming another color‐changing circle. This work provides a good idea for the design of color‐tunable long‐lived organic materials.