Mineral-Edge-Directed Self-Assembly of Fe-Mo-S Interfaces for Groundwater Dehalogenation

Chlorinated organic pollutants in groundwater pose persistent environmental threats due to their chemical stability and resistance to conventional degradation technologies. While iron-based reductants offer theoretical promise, their practical efficacy remains limited by rapid deactivation under groundwater geochemical conditions. Here we demonstrate how natural mineral interfaces can be engineered to overcome these limitations. Through atomic-scale investigation, we reveal that molybdenite (MoS₂) edges serve as geometrically constrained templates for autonomous self-assembly, where Fe(II) preferentially assembles into distorted planar Fe(II)S₄-like coordination motifs at molybdenite edges under alkaline conditions. This edge-directed assembly process establishes stable Fe-S-Mo interfacial bridges that enable sustained electron delocalization, significantly enhancing water activation and hydrogen atom (H*) generation. The resulting catalyst exhibits exceptional dechlorination performance in carbonate-rich groundwater (chloroform degradation rate: 0.336 h^-1) while maintaining high removal efficiency during continuous-flow operation. This work establishes mineral-edge-directed self-assembly as an effective strategy for designing environmentally compatible reductants, bridging fundamental interface science with practical remediation applications.