Plasmon‐Induced Radical‐Radical Heterocoupling Boosts Photodriven Oxidative Esterification of Benzyl Alcohol over Nitrogen‐Doped Carbon‐Encapsulated Cobalt Nanoparticles

Abstract

AbstractSelective oxidation of alcohols under mild conditions remains a long‐standing challenge in the bulk and fine chemical industry, which usually requires environmentally unfriendly oxidants and bases that are difficult to separate. Here, a plasmonic catalyst of nitrogen‐doped carbon‐encapsulated metallic Co nanoparticles (Co@NC) with an excellent catalytic activity towards selective oxidation of alcohols is demonstrated. With light as only energy input, the plasmonic Co@NC catalyst effectively operates via combining action of the localized surface‐plasmon resonance (LSPR) and the photothermal effects to achieve a factor of 7.8 times improvement compared with the activity of thermocatalysis. A high turnover frequency (TOF) of 15.6 h−1 is obtained under base‐free conditions, which surpasses all the reported catalytic performances of thermocatalytic analogues in the literature. Detailed characterization reveals that the d states of metallic Co gain the absorbed light energy, so the excitation of interband d‐to‐s transitions generates energetic electrons. LSPR‐mediated charge injection to the Co@NC surface activates molecular oxygen and alcohol molecules adsorbed on its surface to generate the corresponding radical species (e.g., ⋅O2−, CH3O⋅ and R‐⋅CH‐OH). The formation of multi‐type radical species creates a direct and forward pathway of oxidative esterification of benzyl alcohol to speed up the production of esters.