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

Abstract

Efficient adsorption of gaseous radioiodine is pivotal for the sustainable development of nuclear energy and the long-term radiation safety of the ecological system. However, state-of-the-art adsorbents (e.g. metal–organic frameworks and covalent–organic frameworks) currently under exploration suffer severely 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 mainly determined by the iodine-adsorbent interaction consisting of noncovalent interactions 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 ability of iodine for pre-enrichment 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 exhibit a record-breaking iodine adsorption capacity (2.12 g/g) under dynamic breakthrough conditions and the 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 potential for the nuclear industry.