Lanthanide(III)‐Cu 4 I 4 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)‐Cu 4 I 4 heterometallic organic frameworks (Ln‐Cu 4 I 4 MOFs)‐based X‐ray scintillators are developed by rationally assembling X‐ray absorption centers ([Cu 4 I 4 ] clusters) and luminescent chromophores (Ln(III) ions) in a specific manner. Under X‐ray irradiation, the heavy inorganic units ([Cu 4 I 4 ] 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 Tb 3+ for intense X‐ray‐excited luminescence via excitation energy transfer. The obtained Tb‐Cu 4 I 4 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‐Cu 4 I 4 MOFs is ≈3 times higher than that of the control Tb(III) complex. X‐ray imaging tests show that the Tb‐Cu 4 I 4 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.