Dual–Wavelength Cascade Laser of Highly Emissive Lanthanide Organic Framework

Research into the fluorescence properties of metal–organic frameworks (MOFs) has experienced rapid and sustained advancement in recent years, yet the realization of dual–wavelength emission remains a significant challenge. In this study, we introduce a novel strategy to achieve dual–wavelength cascade lasing by the rational design of lanthanide MOFs. Unlike conventional single–wavelength lasers originating from a dominant transition mechanism, the dual–wavelength behavior reported here is due to several photophysical pathways, including the π–π * transition, metal–to–ligand charge transfer (MLCT), and excited–state intramolecular proton transfer (ESIPT), which operate in tandem within the same framework. Importantly, the energy gap contraction associated with the ESIPT state not only enables the observation of the cascade of dual–wavelength, but also facilitates emission in the near‐infrared II region for the first time. Furthermore, the lanthanide ions incorporated, specifically Tb(III) and Gd(III), serve to enhance the overall luminescence efficiency of the framework through effective sensitization and radiative contribution, resulting in markedly increased emission intensity across the dual channels. As a result, this work provides a versatile approach for the preparation of highly emissive MOFs and expands the functional scope of lanthanide MOFs toward multiwavelength laser applications.