Radioactive waste, such as 90Sr, 134Cs, and 131I, from the Fukushima nuclear spill highlighted the need to find effective adsorbents for scrubbing radioactive ions from seawater. In this issue of Chem, Wang and colleagues report a remarkably 90Sr-selective metal-organic framework (SZ-4) that operates with a two-step ion-exchange mechanism and at a wide pH range while being active and intact when tested in actual seawater.