Pb2ScOF5: A Rare Oxyfluoride with Ultrawide Transparency Enabled by a Differentiated Fluorination Strategy

Incorporating fluoride ions into ordered frameworks that simultaneously and distinctly coordinate with both d0 transition-metal and main-group cations represents a rare phenomenon in oxyfluoride chemistry. Here, we report the first ambient-pressure synthesis of a lead-scandium oxyfluoride, Pb2ScOF5, achieved by a differentiated fluorination strategy. This compound adopts a unique structural topology wherein fluoride ions are selectively coordinated to both rare-earth metal Sc3+ and main-group Pb2+ cations. The structure integrates the wide bandgap characteristics of [ScF6] octahedra with the extended infrared (IR) transparency and optical anisotropy-enhancing properties of distorted [PbO2F3] polyhedra. Interestingly, Pb2ScOF5 exhibits a short UV cutoff at 261 nm (bandgap: 4.31 eV), a wide IR transparency extending beyond 10.4 μm, and a birefringence of 0.038 at 532 nm. To our knowledge, the uncommon combination of UV to IR transparency with appreciable optical anisotropy in a single oxyfluoride crystal is exceptionally rare. This work expands the structural diversity of rare-earth oxyfluorides and highlights an effective structure-guided design strategy for discovering new wide-spectrum optical materials.