Defect-Mediated Bioinspired Coordinatively Unsaturated FeOOH Clusters on ZnO for Efficient Methane-to-Liquid Photooxidation

Direct photocatalytic conversion of methane to oxygenates using molecular oxygen is attractive yet fundamentally constrained by the trade-off between yield and selectivity. Methane monooxygenase (MMO) exemplifies how regulated metal redox cycles and well-defined active sites enable precise and selective C–H activation in methane oxidation. However, constructing enzyme-mimetic sites atomically generally requires complex architectures and costly syntheses, limiting scalability. Here, we report an accessible enzyme-inspired, non-noble photocatalyst constructed by anchoring ultrasmall amorphous FeOOH clusters with coordinatively unsaturated Fe sites onto defective ZnO nanosheets through defect-mediated interfacial interaction. The undercoordinated Fe centers promote side-on O 2 activation while simultaneously enhancing CH 4 adsorption and polarization. The unsaturated Fe sites initiate an MMO-like Fe(II)/Fe(III) redox cycle, regulating ·OH generation for efficient methane activation while restraining deep oxidation. The optimized FeOOH/ZnO achieves an oxygenate yield of 15,974.8 μmol·g –1 with 98.1% selectivity under ambient conditions, significantly surpassing most non-noble catalysts and even some noble-metal benchmarks. This enzyme-inspired strategy offers an effective route to overcome the intrinsic activity–selectivity trade-off in photocatalytic methane-to-oxygenate conversion using earth-abundant metals.