Mild-temperature MOF-to-oxide restructuring constructs Ag-Cu oxide heterojunctions for gas-phase methanethiol oxidation under indoor LED light

초록

Photocatalytic oxidation of volatile organic sulfur compounds under practical indoor lighting is restricted by low light intensity, surface sulfur accumulation, and formation of disulfide byproducts rather than selective oxidation toward CO2 and oxidized sulfur species. Here, we report a mild-temperature, ambient-pressure MOF-to-oxide restructuring strategy to synthesize an MOF-derived Ag-Cu oxide heterojunction (M-ACOH) from a Cu-based metal-organic framework (Cu-MOF) for efficient gas-phase methyl mercaptan (CH3SH) oxidation. Introducing Ag into Cu-MOF under alkaline conditions induces MOF-to-oxide restructuring to form a porous Ag-Cu oxide heterojunction containing CuO, Ag2O, and metallic Ag-related domains. This restructuring increases the specific surface area by 15-fold (825.9 m2 g-1) compared to pristine Cu-MOF and generates defect-rich interfaces, together with broadened visible-light absorption (Eg = 2.2 eV). Under low-intensity white LED irradiation (15 mW cm-2), the M-ACOH achieved 100% CH3SH removal and a CO2 yield of 99.7%, significantly outperforming pristine Cu-MOF and the physically mixed CuO@Ag2O reference. Electron spin resonance and RhB-based radical scavenger tests indicate that M-ACOH effectively suppresses disulfide accumulation by promoting a multi-oxidation network (h+, center dot OH, center dot O2-, and 1O2)-driven pathway, bypassing the inefficient hydroperoxyl (center dot OOH) route observed in Cu-MOF. Furthermore, in situ diffuse reflectance infrared Fourier transform spectroscopy supported a stepwise sequence of CH3SH adsorption/surface coupling, partial oxidation, and deep oxidation toward CO2 and oxidized sulfur species. Post-reaction sulfur analyses via ion chromatography and XPS further revealed the formation of sulfate/oxidized sulfur species, supporting the deep oxidative conversion over M-ACOH. This work provides a mild MOF-to-oxide restructuring approach to design sulfur-affinitive, visible-light-active photocatalysts for low-energy indoor air purification.

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