Radical Negative-Feedback in High Entropy UiO-67 to Break the Activity-Stability Trade-Off in Photocatalytic Oxygenation of CH4.

The activity-stability trade-off has long been a Gordian knot for metal-organic frameworks (MOFs) photocatalyst. Here, a high-entropy UiO-67 MOF (HE-UiO-67) constructed with 2,2'-bipyridine-5,5'-dicarboxylic acid as the linker and ZrCeHfSnFe metal nodes was designed to induce a hydroxyl radical (•OH) negative-feedback mechanism to disentangle the trade-off in methane oxygenation with H2O2. When the •OH concentration generated at Fe sites exceeds the tolerance threshold of adjacent Ce─O bonds, the Ce centers are reconstructed by ligand abstraction into the unsaturated Ce sites for driving the interfacial H2O2 conversion into low oxidative O2 or •OOH species in high-entropy metal nodes, thereby blocking the MOFs damage. This unique radical negative feedback process in HE-UiO-67 can maximize the concentration of radicals while maintain the stable operation for over 100 h in an ambient pressure flow-phase system, substantially exceeding most of the previous reports. Under visible light irradiation, HE-UiO-67 photocatalyst exhibits an outstanding liquid oxygenate yield of up to 9732 µmol g-1 h-1 with a selectivity of 93.5%. Overall, this study opens up a promising strategy for designing efficient and durable photocatalysts to break the activity-stability trade-off in CH4 oxygenation.