Heterogeneous riboflavin-based photocatalyst for pollutant oxidation through electron transfer processes

Organic photocatalysts could employ visible light to produce photodegradation of pollutants; however, their low photostability prevents their reuse even when they are supported on solid materials. Herein, to obtain a Riboflavin (RF)-based photocatalyst robust and recyclable, RF has been covalently anchored to silica particles, converting the known homogeneous photocatalyst into a new heterogeneous one (SiO2-RF). To enhance the photostability of SiO2-RF, generation of the RF triplet excited state and subsequent singlet oxygen were prevented by ensuring a complete shell of RF moieties on the silica spheres. Moreover, adsorption of organic pollutants such as phenol, ortho-phenylphenol, 2,4,6-trichlorophenol and pentachlorophenol on the surface of SiO2-RF is favored in aqueous media, facilitating electron transfer from the pollutants to the short-lived first singlet excited state of RF. Photophysical measurements provided evidence on the photocatalytic mechanism for SiO2-RF.