A Thermally Robust Luminescent Antimony Halide for Real‐Time Detection of Volatile Iodine at Elevated Temperatures

Real‐time monitoring of volatile molecular iodine (I 2 ), a hazardous radioactive byproduct of nuclear processes, is critical for environmental and human safety. Fluorescence quenching offers a promising detection route, but conventional luminophores suffer from thermal instability at operational temperatures. Herein, we report a thermally robust zero‐dimensional antimony halide, [Sr 2 (18‐crown‐6‐ether) 2 (H 2 O) 2 (Cl 2 )]SbCl 5 , as the first luminescent sensor capable of real‐time I 2 detection at elevated temperatures (348 K) in dynamic mode with a limit of detection (LoD) of ∼400 ppb, establishing a benchmark LoD value for high‐temperature iodine sensing via a luminescent technique. This material maintains structural integrity and intense [SbCl 5 ] 2− luminescence at 348 K, which is attributed to hydrogen‐bonding networks that suppress thermal quenching. In addition, the Sb(III) lone pairs serve as electron‐donating sites, capturing I 2 to form polyiodides (i.e., I 3 − and I 5 − ) via electron transfer, which triggers instantaneous luminescence quenching. This work establishes a new paradigm for high‐temperature optical sensors in nuclear safety applications.