In-situ Synthesis of Z-Scheme MIL-100(Fe)/α-Fe2O3 Heterojunction for Enhanced Adsorption and Visible-light Photocatalytic Oxidation of O-xylene

Abstract Though exhibiting excellent performance in the adsorption of organic gas pollutants, the application of MOFs is still limited in the photocatalytic oxidation (PCO) of volatile organic compounds (VOCs) due to the short lifetime of photogenerated electron-hole pairs. MIL-100(Fe)/α-Fe2O3 photocatalysts were fabricated through a facile one-step hydrothermal method by adjusting the coordination of Fe(III) ions for the PCO of typical VOCs. The large specific surface area (763 m2 g−1), uniformly distributed active sites and suitable pore structure of the composites enable the effective adsorption of target o-xylene molecules. The MIL-100(Fe)/α-Fe2O3 hybrid presented a high o-xylene removal efficiency of 100% under 250 W xenon (Xe) lamp irradiation and 90% under visible light (λ ≥ 420 nm), which is far beyond the performance of commercial TiO2 photocatalyst under the same conditions (23% under 250 W Xe lamp irradiation and 0% under visible light). The ESR results confirmed the formation of Z-scheme structure and revealed that the reversible conversion of Fe(III) and Fe(II) under light irradiation plays a key role in the oxidation of o-xylene and the effective generation of reactive radicals. The PCO mechanism of o-xylene was analyzed through in-situ DRIFTS. This work not only provides a means for the synthesis and optimization of high performance photocatalysts based on MOFs for air purification, but also shed light on the PCO mechanism of o-xylene by MOFs photocatalysts.