Reinforced catalytic oxidation of polyoxometalate@charge transfer complex by on-site heating from photothermal conversion

Abstract

Near infrared (NIR) absorption at low energy region has been demonstrated to devoted to photothermal conversion efficiently. This process provides a possibility for valuable extension in emerging photothermal catalysis following a specific approach of molecular composition. To exploit novel photothermal materials in increasing the catalytic activity of comment catalysts, a typical yet unnoticed charge transfer (CT) complex of 3,3′,5,5′-tetramethylbenzidine (TMBCT) is used here as an on-site heater. Through the electrostatic complexation of cationic CT complex bearing strong NIR absorption with series polyanionic clusters, composite catalysts are prepared. These nano-assembled catalysts in size of 5–10 nm display integrated NIR photothermal effect and highly enhanced catalysis for the mild oxidation of toluene and its derivatives into corresponding alcohols with high conversion and selection. While NIR photothermal stability of TMBCT is maintained, the catalytic activity of inorganic clusters is largely improved. The increments in conversion unattainable under external heating condition are realized and the extension to the mild oxidation of thioethers and olefins into sulfoxides and epoxides with acceptable catalytic recyclability and structural stability are demonstrated. All results from the detailed characterizations figure out the applicability of the NIR photothermal conversion to the catalytic reactions with similar catalytic centers.