Hydrogen‐Bond‐Assisted Secondary Amine‐Phosphonate Tandem Sites on Mesoporous Nano‐Silica for Uranyl Carbonate Capture From Alkaline Wastewater

The selective capture of uranium from alkaline radioactive wastewater remains highly challenging because uranyl carbonate complexes, particularly [UO 2 (CO 3 ) 3 ] 4− , possess remarkable thermodynamic stability and electrostatic repulsion from negatively charged adsorbent surfaces. Herein, we report a secondary‐sphere activation strategy by constructing secondary amine‐phosphonate tandem sites within mesoporous nano‐silica channels (GP@SiO 2 ‐APTES) for efficient uranyl carbonate capture. The rationally integrated secondary amine groups and phosphonate moieties establish a cooperative binding microenvironment, in which hydrogen‐bond‐donating secondary amine sites facilitate carbonate activation while adjacent phosphonate groups provide strong uranium coordination. As a result, GP@SiO 2 ‐APTES achieves a remarkable adsorption capacity of 348.8 mg g − 1 toward [UO 2 (CO 3 ) 3 ] 4− under alkaline conditions (pH 8–10), significantly outperforming monofunctional control materials. Combined spectroscopic analyses and density functional theory calculations reveal that the secondary amine‐assisted secondary coordination environment weakens uranyl‐carbonate interactions and promotes phosphonate‐mediated uranium binding. Moreover, the hybrid silica framework exhibits excellent operational durability, retaining over 99% uranium removal efficiency after 250 kGy γ‐irradiation and five adsorption–desorption cycles. This work demonstrates a molecular design strategy that employs hydrogen‐bond‐assisted secondary coordination to facilitate the capture of stable metal complexes, providing new opportunities for advanced actinide separation materials.