Thermally Induced In-Lattice Cation Transformation of 0D Antimony Halides for Improved X-ray Scintillation

Zero-dimensional (0D) organic-inorganic hybrid antimony halides (OISHs), with tunable emission from the blue to near-infrared region, hold great promise as the scintillators for multienergy X-ray imaging. This potential hinges on the unprecedented spectral tunability enabled by cation designability and structural diversity. Herein, for the first time, we report an intriguing thermally induced cation transformation within the lattice of a new 0D OISH, TBTP₂SbCl₅ (TBTP⁺ = (tert-butoxycarbonylmethyl)triphenylphosphonium). This transformation converts TBTP₂SbCl₅ into another new 0D OISH, MLTP₂SbCl₅ (MLTP⁺ = methylenetriphenylphosphonium) and substantially enhances thermal stability (decomposition onset temperature increased from ∼140 to ∼300 °C). Detailed mechanistic studies reveal the transformation pathway: pyrolytic elimination of the bulky ester group followed by decarboxylation. This in-lattice cation tailoring alleviates the structural distortion within the [SbCl₅]^2- polyhedron and weakens excessive electron-phonon coupling, endowing MLTP₂SbCl₅ with comprehensively enhanced scintillation performance: a higher light yield (27,710 vs 17,665 photons MeV^-1), a shorter decay time (3.73 vs 5.06 μs), and a higher spatial resolution (10.1 vs 7.4 lp mm^-1). This work presents the first demonstration of thermally induced in-lattice cation transformation in 0D metal halides and establishes molecular pruning as a new strategy for designing high-performance scintillators.