Enhancing CO photoreduction to CO with 100 % selectivity by constructing heterojunctions and regulating open metal sites in Au/FeO/MIL-101(Fe) catalysts.

The widespread utilization of fossil fuels has resulted in a significant increase in CO emissions, leading to a variety of environmental issues. The photocatalytic conversion of CO into fuel presents an effective solution to both the energy crisis and environmental warming. Therefore, the selection of a suitable catalyst is paramount. However, traditional photocatalysts often encounter challenges such as rapid electron-hole recombination and limited exposure of active sites. To improve these limitations, this study introduces AFM-X, a heterojunction catalyst composed of Au/FeO/MIL-101(Fe)-X, which facilitates the formation of open metal sites (OMS) that enhance the effective separation of photogenerated carriers. In AFM-X, OMS function as Lewis acid sites, thereby enhancing CO adsorption. The presence of Au nanoparticles (NPs) introduces additional active sites for CO reduction. The synergistic effect between OMS and Au NPs increases the catalyst's active sites, while the heterojunction construction promotes electron transfer, thereby enhancing CO photocatalytic reduction efficiency. The CO generation rate of AFM-2 reached 98.8 μmol g h, surpassing those of FM, MIL-101(Fe), FeO, and Au NPs, by 4.1, 6.3, 6.2, and 3.2 times, respectively. Furthermore, AFM-2 maintains stable performance over a 40 h cycle test. In-situ DRIFTS spectroscopy reveals that CO reduction occurs through two parallel pathways. This study offers new insights into the design of composite photocatalytic materials, highlighting the effectiveness of OMS Lewis acid sites in significantly enhancing the photocatalytic reduction of CO.