Superior Iodine Uptake Capacities Enabled by an Open Metal-Sulfide Framework Composed of Three Types of Active Sites

Efficient adsorption of gaseous radioiodine is pivotal for the sustainable development of nuclear energy and long-term safety of the ecological system. However, state of art adsorbents (e.g. MOFs and COFs) currently under exploration severely suffer from limited adsorption capacity, especially under a real-world scenario with extremely low radioiodine concentration and elevated temperature. This mostly originates from the relatively weak sorption driving forces determined by the iodine-adsorbent interaction consisting of non-covalent interactions in major with a small fraction of strong chemical bonding. Here, we document the discovery of an open metal-sulfide framework ((NH4)2(Sn3S7), donated as SCU-SnS) constructed by three different types of active sites as a superior iodine adsorbent. Benefiting from the iodine pre-enrich ability into the framework by charge-balancing NH4+ through N-H⋯I interaction, the efficient reduction of I2 affording I- by S2-, and extremely high binding affinity between Sn4+ and I-, SCU-SnS exhibits record-breaking iodine adsorption capacity (2.12 g/g) under dynamic breakthrough conditions and highest static capacity (6.12 g/g) among all reported inorganic adsorbents both at 348 K. Its facile synthesis and low cost endow SCU-SnS with powerful application potentials in the nuclear industry.