Interlayer phosphate architectonics in porous organic cages enable ultrafast and high-capacity seawater uranium...

Seawater uranium extraction is critical to sustainable nuclear energy. However, porous adsorbents that simultaneously achieve ultrafast kinetics and high capacity remain scarce due to the intrinsic trade-off between ion transport and binding density. Here, a topological design paradigm is introduced by constructing phosphoric adsorption clusters within the interlayer nanospaces of porous organic cages (POCs), yielding the phosphate-functionalized POC (PhosCage). This molecular confinement strategy effectively alleviates the kinetic-capacity limitation prevalent in extended crystalline frameworks. PhosCage achieves exceptional adsorption kinetics, reaching equilibrium within 5 min at lab conditions, and delivers a record capacity of 50.4 mg g^-1 in natural seawater, which is 8.4 times the U.S. DOE baseline. Furthermore, PhosCage maintain stable performance through at least ten adsorption-desorption cycles. Atomic-level mechanistic insights from ToF-SIMS, EXAFS, and DFT reveal that highly localized lone-pair electrons drive strong directional tetradentate coordination with [UO₂(CO₃)₃]^4-, accompanied by substantial charge transfer (1.68 e⁻) and an ultra-high binding energy (-256 kJ mol^-1). This work establishes a molecularly precise blueprint for scalable seawater uranium extraction, and unlocks new avenues for designing efficient adsorbents toward uranium resource recovery and pollution remediation.