Lanthanide(III)‐Cu₄I₄ Organic Framework Scintillators Sensitized by Cluster‐Based Antenna for High‐Resolution X‐ray Imaging

Abstract

Scintillator-based X-ray imaging has attracted great attention from industrial quality inspection and security to medical diagnostics. Herein, a series of lanthanide(III)-Cu₄ I₄ heterometallic organic frameworks (Ln-Cu₄ I₄ MOFs)-based X-ray scintillators are developed by rationally assembling X-ray absorption centers ([Cu₄ I₄ ] clusters) and luminescent chromophores (Ln(III) ions) in a specific manner. Under X-ray irradiation, the heavy inorganic units ([Cu₄ I₄ ] clusters) absorb the X-ray energy to populate triplet excitons via halide-to-ligand charge transfer (XLCT) combined with the metal-to-ligand charge-transfer (MLCT) state (defined as the X/MLCT state), and then the ³ X/MLCT excited state sensitizes Tb³⁺ for intense X-ray-excited luminescence via excitation energy transfer. The obtained Tb-Cu₄ I₄ MOF scintillators exhibit high resistance to humidity and radiation, excellent linear response to X-ray dose rate, and high X-ray relative light yield of 29 379 ± 3000 photons MeV^-1 . The relative light yield of Tb-Cu₄ I₄ MOFs is ≈3 times higher than that of the control Tb(III) complex. X-ray imaging tests show that the Tb-Cu₄ I₄ MOFs-based flexible scintillator film exhibits a high spatial resolution of 12.6 lp mm^-1 . These findings not only provide a promising design strategy to develop lanthanide-MOF-based scintillators with excellent scintillation performance, but also exhibit high-resolution X-ray imaging for biological specimens and electronic chips.