Electrocatalytic Molecular Editing as a New Paradigm for Rare-Earth Separation.

Efficient separation of yttrium from lanthanides remains a persistent challenge due to the limited intrinsic selectivity of molecular extractants. Here, we report an electrocatalytic approach for site-selective functionalization of a high-performance extractant via in situ generated reactive oxygen species. An oxygen-vacancy-rich hollow Bi2O3(S) catalyst selectively produces *OOH intermediates through the two-electron oxygen reduction reaction under mild conditions. These interfacially confined *OOH species act as controllable oxidants to activate the otherwise inert α-methylene site in phosphinoyl phosphonic acid (PPPA), yielding a hydroxylated derivative inaccessible by conventional routes. The modified extractant exhibits enhanced coordination selectivity toward yttrium, resulting in significantly improved separation factors in cascade extraction. Mechanistic studies reveal that oxygen vacancies and interfacial electronic structure cooperatively stabilize *OOH and govern its selective reactivity. This work establishes a general paradigm for coupling electrocatalysis with precision molecular editing, offering a new strategy to overcome long-standing selectivity limitations in separation chemistry.