Breaking the Rigid-Locking Effect: Unlocking Efficient Fenton-Like Reactions for Water Decontamination

Abstract

Overcoming the kinetic bottleneck of Fe(II) regeneration has always been a top priority for enhancing Fenton/Fenton-like processes to degrade emerging contaminants (ECs). In conventional iron-based catalysts (e.g., Fe₂O₃, FeOOH), the iron center is tightly locked inside a rigid cage of hexa-oxygen coordination ([FeO₆] unit) that is resistant to geometric distortion and electron transfer. This phenomenon, termed “Rigid Locking Effect”, hinders the Fe(III)-to-Fe(II) conversion. To break this, we propose a ligand-engineering strategy by partially replacing oxygen coordination with chlorine, featuring a unique [O-FeCl₄–O] motif in laminated reduced graphene oxide (rGO) nanochannels. DFT calculations and Fe XAS spectra reveal that the active [O-FeCl₄–O] unit exhibits “Rigid” breaking, including low reorganization energy, strong electron delocalization, and enhanced spin–orbit coupling (SOC). This tailored motif significantly promotes Fe(II)/Fe(III) cycling, resulting in a turnover frequency per iron site (TOF_Fe) of 43.66 h^–1, which is a 1091-fold enhancement compared to that of the conventional [FeO₆] motif in Fe₂O₃. This enhancement leads to a 30.7-fold increase in HO• yield, enabling efficient removal of diverse ECs in complex water matrices and during long-term continuous operation. This study establishes a proof-of-concept paradigm for designing efficient heterogeneous catalysts and advances practical Fenton-based water decontamination.