Topology‐Driven Conformational Constraint Enables High‐Temperature Organic Phosphorescence

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.