Abstract
Natural gas, consisting mainly of methane (CH₄), has a relatively low energy density at ambient conditions (~36 kJ∙L-1). Partial oxidation of CH4 to methanol (CH3OH) lifts the energy density to ~17 MJ∙L-1 and drives the production of numerous chemicals. In nature, it is achieved by methane monooxygenase with di-iron sites, which is extremely challenging to mimic in artificial systems due to the high dissociation energy of C−H bond in CH4 (439 kJ∙mol-1) and facile over-oxidation of CH3OH to CO and CO2. Here we report the direct photo-oxidation of CH₄ over mono-iron-hydroxyl sites immobilized within a metal-organic framework, PMOF-RuFe(OH). Under ambient and flow conditions using H2O and O2, CH4 is converted to CH₃OH with 100% selectivity and a time yield of 8.81±0.34 mmol∙gcat⁻¹∙h⁻¹ (versus 5.05 mmol∙gcat⁻1∙h⁻1 for methane monooxygenase). By using operando spectroscopic and modelling techniques, we find that confined mono-iron-hydroxyl sites bind CH4 by forming an [Fe−OH···CH4] intermediate, significantly lowering the activation barrier for C−H bonds. The confinement of mono-iron-hydroxyl sites in porous matrix demonstrates a strategy for C−H bond activation in CH4 to drive the direct photosynthesis of CH₃OH.
Original language | English |
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Pages (from-to) | 932-938 |
Journal | Nature Materials |
Volume | 21 |
Early online date | 30 Jun 2022 |
DOIs | |
Publication status | Published - 1 Aug 2022 |
Research Beacons, Institutes and Platforms
- Photon Science Institute
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EPSRC National Research Facility for Electron Paramagnetic Resonance
Collison, D. (Academic lead), Mcinnes, E. (Academic lead), Tuna, F. (Academic lead), Bowen, A. (Academic lead), Shanmugam, M. (Senior Technical Specialist), Brookfield, A. (Technical Specialist), Fleming, E. (Other) & Cliff, M. (Platform Lead)
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