Covalent Phosphazene‐Based Polymers with Fully Heterocyclic Rings for Rapid and Selective Adsorption of Uranium in High Acidity

Abstract Selective uranium adsorption in high acidic conditions is essential and extremely challenging. Based on the potential uranium adsorption capacity of phosphazene‐based frameworks, a design of constructing fully heterocyclic covalent phosphazene‐based polymers (CPPs) is proposed by introducing potential coordination structural units rich in Nitrogen (N), Oxygen (O), and other heteroatoms. The as‐prepared CPP‐N and CPP‐O (CPP‐N/O) with unique ─N═P─NH─C═N‐ and ─N═P─O─C═N─ full heterocyclic structures. Uranium adsorption experiments reveal that under the synergistic coordination of N, O, and other heteroatoms, the saturated sorption capacity of uranium under 1 mol L⁻¹ (M) HNO₃ can reach 270 and 275 mg g⁻¹ for CPP‐N and CPP‐O, respectively. The adsorption capacities of CPP‐N and CPP‐O are greater than 130 and 100 mg g⁻¹at 1‐6 M acidity, respectively. Moreover, the selectivity of CPP‐O for uranium under competing ions can reach up to more than 80%. Both CPP‐N/O show stable and excellent uranium adsorption capacity under high acidity, which lays a path for the design and preparation of novel uranium adsorbents applicable to highly acidic environment.