Carboxyl-Functionalized Carbon Dots as Competent Visible Light Photocatalysts for Aerobic Oxygenation of Alkyl Benzenes: Role of Surface Functionality

Abstract

Carbonaceous nanolights, carbon dots (CDs), are attractive alternatives to semiconducting quantum dots owing to their tunable optoelectronic properties, photostability, biocompatibility, water solubility, etc. Although carbon dot composites with metal or metal oxides have been used as visible light photocatalysts for various organic transformations, the role of surface functionality of unsupported CDs on their photocatalytic activity has not been explored. Reported herein, the efficient activity of carboxyl-functionalized CDs as visible light photocatalysts for the C-H oxygenation of alkyl benzene in the presence of tert-butyl hydroperoxide (TBHP) as an external oxidant. Excellent photoinduced electron transfer properties of CDs coupled with photodecomposition of TBHP resulted in C-H bond oxidation with high activity, selectivity, and recyclability under mild reaction conditions. A comparative evaluation suggested the role of surface traps in charge separation and transport efficiency that could account for the high efficiency of the CDs in the oxidation reactions. © 2018 American Chemical Society.