Abstract
Direct oxidation of methane to valuable oxygenates like alcohols and acetic acid under mild conditions poses a significant challenge due to high C‒H bond dissociation energy, facile overoxidation to CO and CO(2) and the intricacy of C-H activation/C-C coupling. In this work, we develop a multifunctional iron(III) dihydroxyl catalytic species immobilized within a metal-organic framework (MOF) for selective methane oxidation into methanol or acetic acid at different reaction conditions using O(2). The active-site isolation of monomeric Fe(III)(OH)(2) species at the MOF nodes, their confinement within the porous framework, and their electron-deficient nature facilitate chemoselective C‒H oxidation, yielding methanol or acetic acid with high productivities of 38, 592 μmolCH3OHgFe-1h-1 and 81, 043 μmolCH3CO2HgFe-1h-1 , respectively. Experiments and theoretical calculations suggest that methanol formation occurs via a Fe(III)-Fe(I)-Fe(III) catalytic cycle, whereas CH(3)CO(2)H is produced via hydrocarboxylation of in-situ generated CH(3)OH with CO(2) and H(2), and direct CH(4) carboxylation with CO(2).