Fully conjugated radical-doped COF for near-infrared photothermal conversion, C-3 thiocyanation of indoles and oxidative coupling of amines

Abstract

Radical-doped covalent organic frameworks (COFs) have received much interest as it confers additional functions such as photomodulated electrical conductivity, magnetism, and photochromism. Such COFs are relatively underexplored, however, mainly due to the lack of suitable highly photoactive building blocks. Herein, a rare radical-doped fully conjugated COF (PDI-COF) was rationally designed and prepared by incorporating photoactive perylenediimides (PDIs) into its framework. Characterization of the product PDI-COF not only confirmed its porous and stable skeleton, but also revealed the radical derived from photoinduced electron transfer between the PDI and electron donor. The fully conjugated and radical-doped characteristics enable the effective realization of near-infrared photothermal conversion in this COF. Moreover, this radical-doped COF can efficiently generate superoxide radical anions under light irradiation, which promote the photocatalytic C-3 thiocyanation of indoles and the oxidative coupling of amines in high yield and good recyclability at room temperature and without additives. This study demonstrates that introducing a photoactive organic dye into a COF is an effective approach to photothermal conversion materials and metal-free porous photocatalysts for application in photothermal therapy and photocatalytic organic synthesis.