Nanotrap Grafted Anionic MOF for Superior Uranium Extraction from Seawater

Abstract

Abstract On‐demand uranium extraction from seawater (UES) can mitigate growing sustainable energy needs, while high salinity and low concentration hinder its recovery. A novel anionic metal‐organic framework (iMOF‐1A) is demonstrated adorned with rare Lewis basic pyrazinic sites as uranyl‐specific nanotrap serving as robust ion exchange material for selective uranium extraction, rendering its intrinsic ionic characteristics to minimize leaching. Ionic adsorbents sequestrate 99.8% of the uranium in 120 mins (from 20,000 ppb to 24 ppb) and adsorb large amounts of 1336.8 mg g −1 and 625.6 mg g −1 from uranium‐spiked deionized water and artificial seawater, respectively, with high distribution coefficient, K d U ≥ 0.97 × 10 6 mL g −1 . The material offers a very high enrichment index of ≈5754 and it achieves the UES standard of 6.0 mg g −1 in 16 days, and harvests 9.42 mg g −1 in 30 days from natural seawater. Isothermal titration calorimetry (ITC) studies quantify thermodynamic parameters, previously uncharted in uranium sorption experiments. Infrared nearfield nanospectroscopy (nano‐FTIR) and tip‐force microscopy (TFM) enable chemical and mechanical elucidation of host‐guest interaction at atomic level in sub‐micron crystals revealing extant capture events throughout the crystal rather than surface solely. Comprehensive experimentally guided computational studies reveal ultrahigh‐selectivity for uranium from seawater, marking mechanistic insight.