Ultrabright and Water‐Stable Eu(III)‐Based MOF Scintillators Sensitized by Dual‐Antenna Ligands for Real‐Time and Underwater X‐Ray Imaging

Abstract Lanthanide‐based metal–organic framework (Ln‐MOF) scintillators are promising for X‐ray imaging owing to their structural tunability and high X‐ray attenuation. However, achieving efficient triplet‐sensitized scintillation remains challenging due to the inefficient energy transfer between organic ligand triplets and lanthanide centers, leading to weak radioluminescence and limited imaging resolution. Herein, we propose a dual‐antenna ligand strategy by synergizing 4,4′‐oxybis (benzoic acid) (Oba) and phenanthroline derivatives (1,10‐phenanthroline = Phen; or Bathophenanthroline = Bphen) with Eu 3+ ions, constructing ultrabright Eu‐O‐Phen and Eu‐O‐Bphen scintillators. Notably, Eu‐O‐Bphen demonstrated a record relative light yield of 60331 ± 28 photons MeV −1 , outperforming Eu‐O‐Phen by 71%. This superior scintillation performance originates from an 86.3 ± 0.19% photoluminescence quantum yield, attributed to enhanced ligand‐to‐metal energy transfer efficiency and the suppression of π–π stacking among organic chromophore ligands. Besides, the fabrication of flexible Eu‐O‐Bphen films achieves a spatial resolution of 37.0 lp mm −1 in static imaging and enables real‐time dynamic X‐ray imaging at 60 fps (2 K). Additionally, it exhibited exceptional water stability, with negligible performance degradation in water for over 100 days, allowing clear underwater visualization of circuit boards under X‐ray irradiation. It provides a promising strategy for developing high‐performance water‐stable scintillators via ligand engineering.