Visible light-induced Minisci reaction through photoexcitation of surface Ti-peroxo species. Issue 10 (1st April 2021)

• Record Type: Journal Article
• Authors: Naniwa, Shimpei; Yamamoto, Akira; Yoshida, Hisao
• Is Part Of: Catalysis science & technology. Volume 11:Issue 10(2021)
• Page Start: 3376
• Page End: 3384
• Publication Date: 2021-04-01
• Subjects: Catalysis -- Periodicals; 541.395
• DOI: 10.1039/d1cy00248a
• Languages: English
• ISSNs: 2044-4753

Abstract

Abstract : Visible-light induced Minisci-type functionalization of pyridine with tetrahydrofuran proceeds through photoexcitation of surface Ti-peroxo species on TiO2 . Abstract : Photocatalytic Minisci-type functionalization of pyridine with tetrahydrofuran (THF) proceeded using hydrogen peroxide (H2 O2 ) and a TiO2 photocatalyst under acidic conditions. Under UV light ( λ = 360 nm), the reaction selectivity based on pyridine ( S py ) was >99% while the selectivity based on THF ( S THF ) was low such as 19%. In contrast, under visible light ( λ = 400 or 420 nm) S py was similarly high (>99%) and S THF was two times higher than that under UV light. A surface peroxo complex formed upon contact of hydrogen peroxide with the TiO2 surface can be selectively photoexcited by visible light to inject the photoexcited electron to the conduction band of TiO2 . The electron can reduce H2 O2 to a reactive oxygen species (ROS) and promote selectively the Minisci-type cross-coupling reaction between pyridinium ions and THF. A reaction test with a hole scavenger (methanol) evidenced that the hole oxidation of H2 O2 under UV light is responsible for the lower selectivity, in other words, the higher selectivity under visible light would be due to suppression of the hole oxidation of H2 O2 . These results demonstrate a novel way to improve the selectivity of the photocatalytic cross-coupling reaction by using H2 O2 as an oxidant with the photoexcitation of surface Ti-peroxo species on TiO2 .