Modulating the Photocatalytic Activity of Graphene Quantum Dots via Atomic Tailoring for Highly Enhanced Photocatalysis under Visible Light

Precise control over doping of photocatalysts is required to modulate their photocatalytic activity in visible light-driven reactions. Here, a single precursor-employing bottom-up approach is developed to produce different heteroatom-doped graphene quantum dots (GQDs) with unique photocatalytic activities. The solvothermal reaction of a norepinephrine precursor with redox active and condensable moieties effectively produces both nitrogen/sulfur codoped GQDs (NS-GQDs) and nitrogen-doped GQDs (N-GQDs) by simply varying solvents (from dimethyl sulfoxide to water) under microwave irradiation. As-prepared NS-GQDs and N-GQDs show similar lateral sizes (3-4 nm) and heights (1-2 nm), but they include different dopant types and doping constitution and content, which lead to changes in photocatalytic activity in aerobic oxidative coupling reactions of various amines. NS-GQDs exhibit much higher photocatalytic activity in reactions under visible light than N-GQDs and oxygen-doped GQDs (O-GQDs). The mechanism responsible for the outstanding photocatalytic activity of NS-GQDs in visible lightdriven oxidative coupling reactions of amines is also fully investigated.