Tailoring High-Valent Iron-Oxo Species Redox via Extended π-Fe3d-O2p Orbital Overlapping Toward Chemical-Efficient Water Purification.

High-valent iron oxo species (Fe(IV)) are attractive for wastewater treatment because of their high selectivity toward organic pollutants in complex water matrices, but their intrinsic redox properties drive rapid quenching by peroxide precursors, causing excessive chemical consumption. This work addresses this challenge by anchoring Fe(IV) on an iron-phthalocyanine-based conjugated organic framework (FePPC) featuring multi-layered reticular structures and strong π-Fe3d-O2p orbital overlapping. The two-dimensional planar structures provided easily accessible active sites and the extended in-plane conjugation fine-tunes the redox reactivity of surface-confined Fe(IV) species, suppressing unproductive decay while preserving selectivity toward diverse pollutants, yielding a 3.2-fold enhancement in Fe(IV) utilization efficiency. Combined experimental and computational results show that the enhanced orbital overlapping delocalizes electrons at the Fe(IV)═O bond and reduces occupancy of its anti-bonding π* orbital, thereby strengthening the bond against nucleophilic attack by peroxymonosulfate, suppressing O2 evolution, and improving both pollutant selectivity and peroxide stoichiometric efficiency. When integrated into a scale-up membrane reactor, FePPC achieved over 95% micropollutant removal during 72 h of continuous operation. This work fills an important knowledge gap in understanding Fe(IV) redox properties and selectivity, addressing technical bottlenecks in Fe(IV)-based AOP systems toward low-chemical consumption and high-efficiency wastewater treatment.