Lanthanide-Bridged Dual-Atom Catalysts for Efficient Chlorine Electrosynthesis.

The electrocatalytic chlorine evolution reaction (CER) is central to chlor-alkali industries and water treatment, yet its practical deployment is still constrained by high energy demands and insufficient selectivity. Here, we report a "mortise-and-tenon" strategy using a tulip-shaped covalent organic framework (Tu-COF) precursor to construct heteronuclear Ru-Ln dual-atom catalysts (Ln = La, Ce, Pr). The pre-organized micropores of Tu-COF serve as atomic-scale nanoreactors, enabling precise confinement and pairing of Ru and lanthanide atoms. Among them, Ru-Ce delivers outstanding CER performance, achieving 150 mA cm-2 at 1.45 V versus RHE with nearly 100% Faradaic efficiency for Cl2 evolution and over 500 h stability in a flow cell. Mechanistic studies identify the in situ formed RuCeCl-N6 motif as the active site. Density functional theory calculations reveal that adjacent Ce modulates the Ru center's d-band structure and charge distribution, enhancing initial Cl adsorption on RuCe-N6 while optimizing subsequent Cl adsorption on RuCeCl-N6. This lowers the free-energy barrier for Cl-Cl coupling and suppresses competing OOH* formation, thereby accelerating CER kinetics and intrinsically improving activity and selectivity. This work offers a generalizable strategy for heteronuclear DAC construction and highlights lanthanide-mediated electronic engineering as a powerful approach to electrocatalyst design.