Magnetic‐Field‐Assisted Photocatalytic H 2 O 2 Production From Ambient Air via Spin‐Matching‐Mediated Dual Charge Transfer

ABSTRACT Photocatalytic H 2 O 2 synthesis from ambient air is promising but constrained by spin‐forbidden O 2 activation, unidirectional charge injection, and inefficient O 2 mass transport. We introduce a spin‐matching‐enabled dual‐channel cooperative charge delocalization strategy based on a Fe ions and an N,N′‐di(4‐benzoic acid)‐3,4,9,10‐tetracarboxylic acid diimide ligand (Fe‐PDI). The polymer contains mixed‐valence Fe(II)/Fe(III) sites and adopts an intermediate‐spin configuration with a singly occupied axial d z 2 orbital. Experimental and computational results support a dual‐channel Fe–O 2 interaction involving O 2 ‐to‐Fe σ donation and Fe‐to‐O 2 π back‐donation with spin‐aligned electrons filling the O 2 antibonding orbitals, which converts conventional localized unidirectional injection into bidirectional cooperative delocalization. This interaction alleviates spin‐forbidden O 2 activation through a spin‐correlated •O 2 − intermediate while preserving the O─O bond, promotes selective protonation to *OOH, and enhances O 2 surface diffusion and H 2 O 2 desorption. Consequently, with benzylamine as a hole scavenger, Fe‐PDI achieves H 2 O 2 production rates of 19.17 and 23.26 mmol g −1 h −1 without and with an applied magnetic field, respectively, surpassing most reported photocatalytic systems. This work establishes a spin‐charge‐transport synergistic paradigm, offering a generalizable route for spin‐state engineering in single‐site catalysis.