Solid‐Phase Engineered Metal‐Free Carbonized Polymer Dots With Auto‐Generated Rigid Amorphous Network Enabled High‐Temperature Liquid‐Phase Phosphorescence

ABSTRACT While organic phosphorescent materials hold immense promise, their application is severely hampered by limited emission tunability, short lifetimes, and environmental instability. Herein, we report a facile solid‐phase engineering strategy to achieve the large‐scale synthesis of metal‐free carbonized polymer dots (CPDs) from a single precursor. These CPDs feature tunable phosphorescence wavelengths (∼472 to 545 nm) and lifetimes (∼646.49 µs to 65.56 ms), coupled with extraordinary resilience to thermal and moisture stress. Experimental surveys and theoretical calculations reveal that high‐temperature solid‐phase reaction drive the structural evolution of CPDs from amorphous molecules to ordered heptazine structures, enabling the CPDs with progressive singlet‐triplet energy splitting for tunable phosphorescence wavelengths. Concurrently, the auto‐generated rigid amorphous network and hydrophobic groups of CPDs synergistically mitigate triplet exciton quenching triggered by dissolved oxygen and thermal deactivation, endowing the tunable high‐temperature liquid‐phase phosphorescence. With the unique optical characteristics, these CPDs show great promise for applications in aqueous‐phase illumination, displays under harsh conditions, and three‐dimensional information encryption. This work paves a new approach to polymeric phosphorescent materials, significantly contributing to the advanced lighting and information technologies.