Spatially confined Fe2O3 in hierarchical SiO2@TiO2 hollow sphere exhibiting superior photocatalytic efficiency for degrading antibiotics.

We introduce confinement effect to overcome disadvantages of directly immobilizing Fe 2 O 3 on the surface of TiO 2 by encapsulating Fe 2 O 3 in photocatalyst, which exhibits a higher photocatalytic activity. • Spatially confined Fe 2 O 3 in hierarchical SiO 2 @TiO 2 (SFT) photocatalyst was prepared. • A complete degradation of antibiotics was achieved under natural sunlight irradiation. • Transformation intermediates and pathways of antibiotics were presented. • This work provided a new insight for constructing other metal oxides confined photocatalysts. Although TiO 2 -based photocatalysts have achieved great successes for the degradation of organic pollutants, the complete removal of antibiotics is hard to be realized because of its unique macromolecular ring structure under solar-light irradiation. Herein, this work demonstrates the rational design of the hierarchical hollow SiO 2 -Fe 2 O 3 @TiO 2 (SFT) photocatalyst by introducing spatially confined Fe 2 O 3 as a modifier of TiO 2 , in which inner SiO 2 serves as a carrier to support and disperse Fe 2 O 3 in order to obtain small size of Fe 2 O 3 (2–6 nm), while outer TiO 2 acts as a bounding wall to protect Fe 2 O 3 from aggregation and abscission. The as-synthesized SFT photocatalyst not only can overcome easy corrosion, dissolution and deactivation of Fe 2 O 3 during the photoreaction process, but also can substantially enhance the adsorption of antibiotics because of its hierarchical hollow structure, facilitating the separation of electron-hole pairs and prolonging the trapping of incident light. Therefore, the SFT photocatalyst manifests the complete removal of antibiotics under simulated solar light irradiation. The intermediates of antibiotics were analyzed by liquid chromatography-mass spectrometry (LC/MS) and the possible degradation pathway was proposed accordingly. Besides, SFT photocatalyst exhibits an excellent recyclability due to confinement effect. Especially, the as-synthesized SFT also achieves the 100% degradation rate of antibiotics under natural sunlight irradiation, efficiently overcoming the incomplete removal of antibiotics for many previous TiO 2 -based photocatalysts. [ABSTRACT FROM AUTHOR]