Radioactive waste, such as Sr-90, Cs-134, and I-131, 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 Sr-90-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.