Organic Cation Engineering of Coordination Frameworks for Thermally Robust Copper(I) Iodide Cluster Scintillators

Cu(I) cluster scintillators are highly promising for X-ray imaging and high-energy particle detection, owing to their high light yield, tunable photophysical properties, diverse composition and structure, and facile synthesis. However, as organic–inorganic hybrids, most Cu(I) clusters feature intrinsically soft lattices that render them susceptible to severe thermal quenching, which restricts their potential application in high-temperature X-ray imaging. Herein, we synthesize two Cu(I) cluster single crystals, namely, Cu4I6–SICF (soft ionic-coordination framework) and Cu4I4–RCF (rigid coordination framework), and study their structure–property relationship. Compared with Cu4I6–SICF, Cu4I4–RCF exhibits a higher crystal hardness of 0.35 GPa and a weaker electron–phonon coupling of 125 meV. This enhanced structural rigidity contributes to the suppressed molecular vibrations and structural relaxation at elevated temperatures. Consequently, the Cu4I4–RCF scintillator retains a high radioluminescence intensity of 90% at 373 K and 75% at 453 K, and achieves a broad operating temperature range from 77 to 453 K, ranking it among the highest-temperature Cu(I) cluster scintillators reported to date. Benefiting from its excellent light yield and spatial resolution, the Cu4I4–RCF scintillator enables high-temperature X-ray imaging for chip inspection applications. This study underscores the critical role of structure–property relationships in developing thermally stable Cu(I) clusters for high-temperature applications.