Crown Ether-Incorporated Metal Halides Unify High-Performance Iodine Capture with Built-In Optical Monitoring of Adsorption Process

The management of radioactive iodine, a typical fission product released in the nuclear fuel cycle and nuclear accidents, demands not only a deep decontamination capability but also reliable monitoring of adsorbent status. However, this critical need is yet unrealized by conventional sorbents. To bridge this gap, we propose a design strategy that integrates iodine adsorption with intrinsic optical properties within a series of zero-dimensional crown ether-based cuprous halide clusters (Cu-I-18C6-BnCl and Cu-X-18C6-PDA, X = I/Br/Cl, BnCl = protonated 4-chloroaniline ion, PDA = protonated 1,3-propanediamine ion). In these hybrids, both the crown ether-amine motifs and CuX clusters act as efficient iodine-binding sites, while the luminescent CuX clusters serve as stimuli-responsive optical sensors. The organic-inorganic hybrid metal halide Cu-Cl-18C6-PDA exhibits an exceptional iodine vapor adsorption capacity of 3.27 g·g-1, even rivaling conventional porous adsorbents. More strikingly, Cu-I-18C6-BnCl exhibits complete and irreversible fluorescence quenching exactly at the adsorption breakthrough point during dynamic flow experiments, providing an unambiguous visual signal of column saturation without the need for instrumentation. This work integrates an efficient iodine adsorbent and sensor within zero-dimensional (0D) crown ether-functionalized cuprous halide clusters, advancing smart adsorbent systems for nuclear waste treatment and environmental remediation.