Semi-Ionic C-F Bonds Modulate Hydrogen Dynamics for Selective CO₂-to-CH₄ Electroreduction on Carbon Quantum Dots

Electrochemical CO₂ reduction to CH₄ represents an attractive route for carbon recycling and energy storage, but remains limited by sluggish hydrogenation kinetics and ineffective management of reactive hydrogen species. Herein, we develop a molecular fusion strategy to synthesize fluorine-rich carbon quantum dots (F1-CQDs) featuring an unprecedented F content of up to 28.8 at. % in optimized F1-CQDs. The catalyst delivers a CH₄ Faraday efficiency of 63.2% together with a CH₄ partial current density of 210.8 mA cm^-2 in a flow cell. Combined in situ spectroscopy and theoretical calculations reveal that semi-ionic C-F bonds create abundant Lewis basic sites that selectively stabilize key CO₂-reduction intermediates, while also regulating hydrogen dynamics by facilitating water activation and transient active hydrogen (*H) formation on neighboring carbon sites. This synergistic dual-site functionality enhances the effective *H availability for stepwise hydrogenation without excessively favoring the competing hydrogen evolution reaction, as clarified by isotope labeling and *H-scavenging experiments. This work establishes a clear structure-activity relationship between C-F bonding and catalytic performance, and provides a general design principle for metal-free electrocatalysts through the coupled engineering of intermediate stabilization and hydrogen kinetics.