Sulfone Molecular Switch Enables Direct Two-Electron Uranium Photoreduction in Programmed Covalent Organic Frameworks

Photocatalytic uranium extraction from seawater is indispensable for sustainable nuclear energy, yet its efficiency is fundamentally limited by the prevailing indirect superoxide-mediated reduction pathway, which suffers from sluggish kinetics, oxygen dependency, and poor selectivity. Herein, it is demonstrated that a molecular-level "sulfone switch", integrated into a covalent organic framework via edge-hanging engineering, orchestrates a decisive shift from the indirect to a direct two-electron transfer pathway for uranium photoreduction. The optimized Py-DaSO-COF achieves a remarkable uranium extraction capacity of 21.25 mg g^-1 in natural seawater, which is coupled with rapid kinetics and high selectivity against vanadium ions, surpassing most reported photocatalytic systems. Notably, combined experimental and theoretical studies reveal that the electron-deficient thiophene sulfone group promotes exciton dissociation, stabilizes key *UO₂ intermediates, and suppresses •O₂ ^- generation by diverting electrons directly to adsorbed uranium species. This work establishes a versatile molecular engineering strategy for controlling photocatalytic pathways, highlighting its universal significance for solar-driven resource recovery and beyond.