Rigidifying Symmetry-Broken Cu4I4 Clusters with Hydrogen-Bonded Frameworks Enables Fast and High Light Yield Scintillation for Real-Time Dynamic X-ray Imaging and 3D Tomographic Reconstruction

Lead-free metal-halide scintillators commonly face a fundamental compromise that electronic symmetry breaking is desirable for efficient triplet harvesting, yet it often softens the lattice and amplifies nonradiative losses. Here we address this conflict by coupling symmetry-lowered electronic structure with supramolecular rigidification in a Cu-I cluster scintillator. Solvent-directed coordination replaces one bulky tris(2-furyl)phosphine (TFP) ligand with CH ₃ CN to form an asymmetric cubane, Cu ₄ I ₄ (TFP) ₃ CH ₃ CN, whose exposed iodide-rich face is locked by a hydrogen-bonded framework featuring abundant core-anchoring I···H contacts. Crystallographic and Hirshfeld analyses reveal markedly enhanced core-involving short contacts relative to the symmetric analogue Cu ₄ I ₄ (TFP) ₄ , rationalizing the suppressed excited-state structural relaxation. The symmetry-lowered electronic manifold reduces ΔE _ST to 0.062 eV and enables essentially complete thermally activated delayed fluorescence, affording a quantum efficiency of 92.9% with a fast decay of 3.77 µs. Under X-ray irradiation, Cu ₄ I ₄ (TFP) ₃ CH ₃ CN delivers a light yield of 59819 photons MeV ^− 1 and a detection limit of 51.2 nGy s ^− 1 , far exceeding the symmetric Cu ₄ I ₄ (TFP) ₄ . PVP-assisted processing further enables flexible scintillator screens with 28 lp mm ^− 1 resolution for radiography, tomographic reconstruction, and real-time dynamic imaging. This work highlights supramolecular confinement as an effective route to maximize scintillation efficiency in electronically symmetry-broken Cu-I cluster emitters.