Embedded Hard Base Sites in 1D Covalent Organic Frameworks Enable Selective Photocatalytic Uranium Recovery from Rare Earth Leaching Solution

Abstract Selective uranium recovery from rare earth leaching solutions is hindered by competing ions and similar chemistry. Herein we propose a “framework-embedded hard base sites” strategy that simultaneously resolves selectivity and charge separation bottlenecks. By anchoring oxygen atoms as hard bases into 1D covalent organic frameworks (COFs), we create a dual-function platform where oxygen sites selectively capture uranyl ions while delocalizing excitons, lowering the exciton binding energy to 56.2 meV. The optimal COF-PODA with the highest density of oxygen sites achieves a high adsorption capacity of 1205 mg g–1 and reduction kinetics of 0.079 min–1. In actual rare earth leaching solution, it removes 99.5% of uranium with outstanding selectivity over lanthanides and retains more than 95% activity after six cycles. This work uncovers an unforeseen synergy between hard-base coordination and electronic modulation, establishing a new design route for advanced radionuclide photocatalysts.