Redox-Active Antimony Sulfide Frameworks for Dynamic Radioiodine Capture

Efficient capture of radioactive iodine is crucial for nuclear safety and environmental protection, yet it remains challenging under dynamic, high-temperature off-gas conditions. Herein, we systematically evaluated the in-depth iodine removal performance of two antimony sulfide frameworks, a 2D-layered and a 3D-channeled architecture (denoted as the 2D-Sb₂S₃ framework and 3D-Sb₂S₃ framework), featuring electron-rich sulfide sites and soft Lewis acid antimony ions. Both materials exhibit modest static iodine uptake capacities (3.32 and 3.12 g g^-1, respectively), while the 3D framework achieves a superior dynamic capacity of 1.25 g g^-1 at 373 K, outperforming benchmark materials such as SCU-SnS (0.88 g g^-1) and Ag-loaded silica gel (0.54 g g^-1). The application potential of the 3D framework was further confirmed by the continuous accumulation of ¹³¹I₂ in a radioactive dynamic adsorption setup. Mechanism analysis combined with powder X-ray diffraction, X-ray photoelectron spectroscopy, and time-dependent Raman spectroscopy reveals that iodine uptake proceeds via multiple pathways, including charge-transfer interactions with incorporated macrocyclic polyamines and the redox-induced formation of SbI₃. This work introduces a new design paradigm for redox-active metal sulfide adsorbents by leveraging soft acid/base interactions and framework reactivity, offering a viable approach for advanced iodine capture in nuclear waste management.