ZIF-67-Confined Fe Nanoclusters for Integrated Faradaic Deionization and Water Sterilization

Abstract

Electrochemical water purification technologies capable of performing desalination and disinfection within a single process unit represent a transformative solution to the global challenge of freshwater scarcity. However, the rational integration of these two functions at the electrode level is fundamentally constrained by the divergent material requirements for efficient faradaic ion storage and robust electrocatalytic oxidant generation. Here, we demonstrate that sub-nanometer iron nanoclusters (Fe NCs) spatially confined within a zeolitic imidazolate framework (ZIF-67) via a pore-mediated vapor diffusion (PVD) strategy reconcile these competing demands within a single electrode architecture. The nanoconfinement of Fe NCs within the ZIF-67 micropores serves a dual purpose: it drastically shortens the solid-state chloride-ion diffusion pathways, enabling ultrafast faradaic charge storage with exceptional cycling stability, while simultaneously creating highly active catalytic sites for the continuous in situ electro-generation of reactive oxygen species (ROS) and reactive chlorine species (RCS). Of note, the electrode operates as a “capture-and-kill” platform, wherein negatively charged bacteria are electrostatically enriched at the anode surface and subsequently eradicated by the locally generated oxidative species, with dead cells desorbing during electrode regeneration. The optimized Fe NCs@ZIF-67 electrode delivers a competitive desalination capacity of 49.3 mg g-1, an ultrafast desalination rate of 0.31 mg g-1 s-1, and nearly 100% capacity retention over 20 cycles, while achieving the efficient inactivation of Escherichia coli. This work offers a nanoconfinement-driven blueprint for designing multifunctional electrodes that bridge the longstanding divide between electrochemical desalination and water disinfection.