Mapping the Surface Groups of Amine-Rich Carbon Dots Enables Covalent Catalysis in Aqueous Media

Carbon nanodots stand as the missing link between the molecular and the nanoscale world, owing to the unique molecular-like behavior emerging from their synthetic precursors. A converging set of analytical and spectroscopic data yields a precise inventory of the surface reactive groups of amine-rich carbon dots (NCDs-1). As a result, NCDs-1 provide a multi-functional nano-platform that is able to covalently activate carbonyl groups, form iminium-ions and enamine intermediates, and efficiently promote diverse aminocatalytic transformations in water. Remarkably, the catalytic activity of carbon dots can also govern the stereoselectivity in the bond-forming event. Indeed, the use of chiral carbon dots (NCDs-7) as catalysts affords the final aldol products with significant enantiomeric excess. The successful implementation of carbon nanostructures into chemical roles so far restricted to molecular systems opens new avenues for advanced applications where the nanoscale and the molecular realms will merge and complement each other.