Topology‐Driven Conformational Constraint Enables High‐Temperature Organic Phosphorescence

ABSTRACT Achieving organic phosphorescence that remains stable at elevated temperatures is challenging because thermally activated molecular motions typically accelerate non‐radiative decay of triplet excitons. Here, we report a topology‐driven conformational constraint strategy to enable high‐temperature organic phosphorescence. A hydrogen‐bonded supramolecular framework constructed from melamine and terephthalic acid serves as a rigid scaffold that imposes topological confinement on embedded terphenyl‐based emitters. Comparative studies using emitters with linear, bent, and trigonal‐like geometries reveal a clear geometry‐dependent trend in phosphorescence performance, suggesting that increased connectivity within the hydrogen‐bonded network strengthens conformational constraint and reduces non‐radiative relaxation pathways. Consistent with this topology–phosphorescence relationship, the system integrating trigonal‐like emitters exhibits persistent phosphorescence with a lifetime of up to 1.22 s at room temperature and retains long‐lived emission of 344 ms even at 150°C. Benefiting from the excellent environmental stability, the phosphorescent materials can be integrated into polymer matrices to fabricate flexible luminescent films that operate under high‐temperature conditions. This work highlights topology‐driven conformational constraint as an effective design strategy for developing environmentally robust organic phosphorescent materials.