Dual-Atomic Fe Sites with d−d Orbital Coupling for Efficient Conversion of Benzene to Phenol

Heterogeneous dual-atom catalysts (DACs) are promising due to synergistic effects, but precise synthesis with defined electronic structures and high metal loading remains challenging. Herein, we report Fe-based DACs with Fe loadings up to 9.7 wt %, which significantly improve the catalytic activity in direct benzene-to-phenol oxidation using H 2 O 2 at room temperature compared to the single-atom counterpart ( i.e., Fe/NC). Specifically, Fe 2 /NC achieved a benzene conversion of 92.3%, which is 6.3 times higher than that of Fe/NC (12.3%) under the same conditions, without sacrificing phenol selectivity (96.2% (Fe 2 /NC) vs 99.4% (Fe/NC)), making it among the best Fe-based catalysts reported to date. Meanwhile, the calculated TOF of Fe 2 /NC (190.0 h −1 ) is 3 times that of Fe/NC (64.5 h −1 ), further highlighting the significantly enhanced intrinsic activity of dual-atom sites. In situ ATR-IR spectra and DFT calculations reveal Fe−O species as the active sites and a distinct reaction pathway governed by Fe−Fe d−d orbital coupling. This electronic interaction upshifts the d-band center while selectively enhancing d xy and d z 2 orbital exposure near the Fermi level, strengthening hybridization with O-2p orbitals and benzene π systems. These synergistic effects lower the barrier of the rate-determining step and stabilize transition states. This work establishes an electronic orbital-level structure−activity relationship, emphasizing the crucial role of dual-atom sites.