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

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.