Fe-O Clusters Anchored on Nodes of Metal-Organic Frameworks for Direct Methane Oxidation

Direct methane oxidation into value-added organic oxygenates with high productivity under mild condition remains a great challenge. We show Fe-O clusters on nodes of metal-organic frameworks (MOFs) with tunable electronic state for direct methane oxidation into C1 organic oxygenates at 50 degrees C. The Fe-O clusters are grafted onto inorganic Zr-6 nodes of UiO-66, while the organic terephthalic acid (H2BDC) ligands of UiO-66 are partially substituted with monocarboxylic modulators of acetic acid (AA) or trifluoroacetic acid (TFA). Experiments and theoretical calculation disclose that the TFA group coordinated with Zr-6 node of UiO-66 enhances the oxidation state of adjacent Fe-O cluster due to its electron-withdrawing ability, promotes the activation of C-H bond of methane, and increases its selective conversion, thus leading to the extraordinarily high C1 oxygenate yield of 4799 mu mol g(cat)(-1) h(-1) with 97.9 % selectivity, circa 8 times higher than those modulated with AA.

Automated summary

By tuning the Fe-O clusters and ligands of UiO-66 within metal-organic frameworks (MOFs), direct oxidation of methane to C1 organic oxygenates at 50 degrees Celsius can be achieved, with Zr-6 nodes coordinated with TFA modulators enhancing the oxidation state of Fe-O clusters and significantly increasing the productivity and selectivity of the reaction.