Visible-light induced selective oxidation of sulfides by hierarchical benzothiadiazole-based polymers

Abstract

By using 4,7-dibromo-2,1,3-benzothiadiazole as photoactive group, the Sonogashira coupling between 4,7-dibromo-2,1,3-benzothiadiazole and 1,3,5-triethynylbenzene results in benzothiadiazole functionalized conjugated microporous polymer (CMP), named CMP-3-BT. The obtained CMP-3-BT shows hierarchical structures, which consists of microspheres and curved nanobelts. Moreover, CMP-3-BT is semiconductive porous materials with band gap of 2.24 eV. By using 425 nm LED (3 W) as light source, assisted by H2O2, CMP-3-BT enables the oxidation of thioanisole bearing various substituents to their corresponding sulfoxides under O2 atmospheres at room temperature with high efficiency and excellent selectivity. EPR spectra indicate that the 1O2 and O·- 2 are the active oxygen species for the photo-oxidation of thioanisole. Importantly, the catalytic activity of CMP-3-BT remains unchanged after 6 cycles, indicating the excellent structural stability and catalytic activity of CMP-3-BT serving as a reusable green catalyst.

Keywords

• conjugated microporous polymer
• visible-light mediated catalysis
• benzothiadiazole
• sonog-ashira coupling reaction
• sulfide oxidation