A Smart Biomimetic Supramolecular Adsorbent for Dynamic Radiocesium Capture from Contaminated Water

Sequestering radioactive 137Cs from contaminated water is crucial for nuclear wastewater management, emergency radiological response, and long-term protection of water resources. However, selectively removing 137Cs in complex water systems remains challenging because it exists as highly soluble, weakly coordinating 137Cs+ and typically coexists with overwhelming concentrations of competing ions. Here we report ZJU-X66, an anionic indium-based metal-organic framework featuring a supramolecular Venus flytrap-like structure. ZJU-X66 exhibits rapid and highly selective 137Cs+ uptake under authentic radioactive conditions, reaching sorption equilibrium within 5 min and achieving >98% removal within 10 min in West Lake water. It further delivers an exceptional Kd value for 137Cs+ exceeding 107 mL/g in pure water within 30 min, while retaining a Kd value above 105 mL/g across diverse aqueous matrices, placing it among the top-performing reported 137Cs+ sorbents. ZJU-X66 is regenerable over five cycles, withstands β and γ irradiation up to 200 kGy, and treats ca. 3,900 bed volumes in continuous flow before breakthrough. Mechanistic studies combining ssNMR, XAFS, TOF-SIMS, in situ vibrational spectroscopy, SCXRD, MD simulations, and DFT calculations provide dynamic molecular-level evidence for a smart guest-responsive capture process, in which Cs+ selectively triggers framework contraction and cavity closure for adaptive physical encapsulation. This work establishes a rare dynamic recognition, closure, and encapsulation strategy for radioactive 137Cs+ remediation.