High-spin surface FeIV = O synthesis with molecular oxygen and pyrite for selective methane oxidation

Abstract

Nature-inspired high-spin Fe^IV = O generation enables efficient ambient methane oxidation. By engineering sulfur-bridged dual ≡Fe^II…Fe^II≡ sites on pyrite (FeS₂) mimicking soluble methane monooxygenase, we achieve O₂-driven formation of high-spin (S = 2) surface Fe^IV = O species at room temperature and pressure. Strategic removal of bridging S atoms creates active sites that facilitate O₂ activation via transient ≡Fe-O-O-Fe≡ intermediates, promoting homolytic O − O bond cleavage. The resulting Fe^IV = O exhibits an asymmetrically distorted coordination environment that reduces the crystal field splitting and favors the occupation of higher energy d-orbitals with unpaired electrons. Impressively, this configuration can efficiently convert CH₄ to CH₃OH through an oxygen transfer reaction with a synthetic efficiency of TOF = 27.4 h⁻¹ and selectivity of 87.0%, outperforming most ambient O₂-driven benchmarks under comparable conditions and even surpassing many H₂O₂-mediated systems. This study offers a facile method to synthesize high-spin surface Fe^IV = O and highlights the importance of metal spin state tailoring on non-enzymatic methane activation.