Isomerization Engineering of Oxygen-Enriched Carbon Quantum Dots for Efficient Electrochemical Hydrogen Peroxide Production.

Hydrogen peroxide (H2O2) has emerged as a kind of multi-functional green oxidants with extensive industrial utility. Oxidized carbon materials exhibit promises as electrocatalysts in the two-electron (2e-) oxygen reduction reaction (ORR) for H2O2 production. However, the precise identification and fabrication of active sites that selectively yield H2O2 present a serious challenge. Herein, a structural engineering strategy is employed to synthesize oxygen-doped carbon quantum dots (o-CQD) for the 2e- ORR. The surface electronic structure of the o-CQDs is systematically modulated by varying isomerization precursors, thereby demonstrating excellent electrocatalyst performance. Notably, o-CQD-3 emerges as the most promising candidate, showcasing a remarkable H2O2 selectivity of 96.2% (n = 2.07) at 0.68 V versus RHE, coupled with a low Tafel diagram of 66.95 mV dec-1. In the flow cell configuration, o-CQD-3 achieves a H2O2 productivity of 338.7 mmol gcatalyst -1 h-1, maintaining consistent production stability over an impressive 120-hour duration. Utilizing in situ technology and density functional theory calculations, it is unveil that edge sites of o-CQD-3 are facilely functionalized by C-O-C groups under alkaline ORR conditions. This isomerization engineering approach advances the forefront of sustainable catalysis and provides a profound insight into the carbon-based catalyst design for environmental-friendly chemical synthesis processes.

Lanthanide-Catalyzed Tandem Insertion of Secondary Amines with 2-Alkynylbenzonitriles: Synthesis of Aminoisoindoles.

A lanthanide-catalyzed intermolecular hydroamination of 2-alkynylbenzonitriles with secondary amines has been disclosed, providing a streamlined access to a range of aminoisoindoles in moderate to excellent yields. The salient features of this reaction include high bond-formation efficiency, mild reaction conditions, 100 % atomic efficiency and good functional group tolerance. This methodology has also been successfully applied to the construction of other nitrogen-containing compounds, such as 5 H-imidazo[2,1-a]isoindoles and isoquinolines. A plausible mechanism for the formation of aminoisoindoles involving initial N-H activation by a lanthanide complex followed by C≡N insertion into a Ln-N bond to form an amidinate lanthanide intermediate, which undergoes the cyclization is proposed.