Synthesis of sub-nanometric Cu2O catalysts for Pd-free C-C coupling reactions

We report a facile solution-phase sonochemical route for the glucose-template mediated synthesis of Cu2O nanocrystals with well-defined sizes and shapes. This approach offers a superficial and cost-effective route for the synthesis of Cu2O nanocrystals. The formation of different nanostructures (i.e., stars, cubes, and octahedra) was tuned by varying the reaction conditions as well as the concentration of template. The morphology-controlled Cu2O nanocrystals show high activity for the external base-free Ullmann homocoupling reactions of aryl halides. 61.6% conversion of chlorobenzene was achieved over octagonal Cu2O nanocrystals with a turn-over-frequency (TOF) as high as 1696 h(-1). This result demonstrates that the size and shape-dependent properties of Cu2O nanocrystals are critical to the activity of aryl halide and highlights the importance of shape engineering in the design and development of an efficient catalyst for the Ullmann reaction.