Spin State Crossover of an Fe1 Single-Atom Catalyst for Promoted Methane Conversion to Oxygenates under Mild Conditions

Abstract Engineering the electronic and spin states of active centers for promoted oxygenate production from methane remains a fundamental challenge in catalysis. Herein, we demonstrate that spin crossover of Fe1 single-atoms from high spin (HS) to low spin (LS) could boost the oxygenate yield by 5.3-fold. The spin transition is realized by coordinating Fe1 sites with strong-field ligand carbon monoxide (CO). Compared with traditional L-FeHS-O (L = H2O) motifs, low-spin L-FeLS-O (L = CO) with CO coordination introduces unoccupied O 2p states near the Fermi level and increases electron density on the oxygen center. The resulting enhancement in electrophilicity of the oxo center facilitates hydrogen abstraction from methane, lowering the C−H activation barrier from 1.26 eV to 0.65 eV. Consequently, an oxygenate productivity of 1615.3 mmol gFe−1 h−1 with ∼100% selectivity is achieved at 30 °C. The strategy of spin regulation paves an avenue for designing prospective single-atom catalysts toward efficient methane valorization.