Interfacial hydride transfer for dehalogenation with water.

Reductive dehalogenation of organohalides through hydrodehalogenation with water is critical for environmental and chemical industries. Conventional hydrodehalogenation proceeds via electron transfer pathways (e.g., stepwise electron/hydrogen radical transfer, or two-electron transfer followed by protonation), which are often hampered by limited dehalogenation kinetics and selectivity. While the interfacial transfer of reductive hydride (Hδ-) species presents a compelling concerted two-electron pathway, its application has been constrained by the difficult surface hydride formation under mild conditions. Here, we overcome this challenge by developing mechanochemically activated zero-valent iron (ZVI) that generates reactive silicon-hydride (Si-Hδ⁻) species in the presence of trace water. Trace water induces ZVI corrosion to produce H2, which is heterolytically cleaved by in situ formed surface Siδ+-Oδ⁻ Lewis pairs, yielding nucleophilic Si-Hδ⁻ motifs. These motifs drive direct interfacial hydride transfer for highly efficient hydrodehalogenation and regioselective deuteration with rate constants 2-50 times greater than conventional radical-based hydrogen transfer on ZVI. The water-mediated regeneration of the hydride donor enables continuous-flow decontamination of actual halogenated groundwater and valorization of organohalides into high-purity deuterated products with selectivity of 93.4%. This work presents a promising mechanochemical platform that suggests a more sustainable approach for selective hydrodehalogenation of organohalides.