Supramolecular Assembly of Cesium Copper Iodine Resulting in Rich Emission Properties

Abstract Crown ether‐assisted supramolecular assembly is a robust strategy for manipulating low‐dimensional metal halides. In this study, the supramolecular assembly of 0D‐Cs 3 Cu 2 I 5 is presented. Upon the addition of 15‐crown‐5 (15C5) to Cs 3 Cu 2 I 5 , 15C5 immediately coordinates with Cs + to form the cone‐shaped [(15C5)Cs] + . Simultaneously, one of the iodine atoms is removed from the [Cu 2 I 5 ] 3‐ cluster, resulting in the formation of a sub‐planar rhombic [Cu 2 I 4 ] 2− unit. This process leads to white emission, specifically [(15C5)Cs] 2 [Cu 2 I 4 ], which exhibits a photoluminescence quantum yield (PLQY) close to unity. The [(15C5)Cs] + further reacts with 15C5 to form the sandwich‐type cationic structure [(15C5) 2 Cs] + , accompanied by the generation of red emission [(15C5) 2 Cs] 2 [Cu 2 I 4 ]. By carefully controlling the amount of 15C5, various emission composites can be achieved, particularly tunable white emission. The assembly process is reversible. The pristine Cs 3 Cu 2 I 5 can be recovered after thermal curing because of the volatility of crown ether and the weak Cs‐crown ether bond. Theoretical calculations have demonstrated that the coordination of the crown ether primarily affects the energy level, leading to changes in the excited state and photophysical properties. The applications in anticounterfeiting and LED phosphors have been demonstrated. This work provides a new approach for the development of low‐dimensional copper halides with promising applications in optoelectronics.