Hydrogen-Bonded Organic Framework-Confined Carbon Dots toward Efficient Red Room-Temperature Phosphorescence via Resonance Energy Transfer

Room-temperature phosphorescence (RTP) materials are promising for information encryption and anticounterfeiting. However, realizing long-wavelength RTP of carbon dots (CDs) is challenging owing to unstable triplet states and strong nonradiative decay. Herein, we construct a hydrogen-bonded organic framework (HOF) through molecular self-assembly and realize the in situ generation of CDs within the HOF matrix. By further incorporating Rhodamine B (RhB) into the HOF, a donor–acceptor resonance energy transfer (RET) system is established, enabling efficient red RTP emission. In this system, the HOF matrix provides a confined environment for the CDs and RhB. Meanwhile, the hydrogen-bonded network restricts excited-state molecular motions and suppresses nonradiative relaxation. The optimized CDs-RhB@HOF composite exhibits outstanding red phosphorescence centered at 600 nm, achieving a high PLQY of 34.20% (versus 0.71% for CDs@HOF) and a prolonged lifetime of 458 ms. The composite material has been successfully applied to multilevel anticounterfeiting encryption.