Nano‐Multiactive Sites Pd/PdO/CuO/PdCu₃ Formed In Situ on the Surface Hetero‐Organometallic Pd(II)/Cu(II) Nanosheet: Investigation on the Formation of Active Sites, Synergistic, and Catalytic Activity

Abstract

Exploring the relationship between the structure of active site and the activity in molecular level and investigating the reason for deactivation are extremely important in designing the highly active catalyst. In this paper, new self‐assembly Schiff‐base Pd/Cu nanosheets supported on the surface of graphene oxide (GO) (called as GO@Hpmaba‐Pd/Cu) were fabricated and characterized. Among them, GO@Hpmaba‐Pd0.2/Cu0.8 exhibited a high activity with a TOF value of up to 95,357 h−1 and substrate suitability in Suzuki cross‐coupling reaction. GO@Hpmaba‐Pd0.2/Cu0.8 could be reused at least 13 times. GO@Hpmaba‐Pd0.2/Cu0.8 was a heterogeneous catalyst and the catalysis occurred on the surface. The truly active sites included Pd/PdO/CuO/PdCu3 formed in situ on the surface of the hetero‐organometallic Pd/Cu nanosheet during catalysis. The synergistic effects among these active sites could be described as that the electrons transferred from GO to CuO (PdO) or to Pd via ligand (Hpmaba) and subsequently electrons transferred from CuO (PdO) to Pd. These made more electron negative palladium, enhancing the oxidation addition between palladium and aryl halide and prompting the activity. The deactivation of catalyst was mainly caused by some destroyed organometallic in the nanosheet, residues adsorbed on catalytic surface, loss of active Pd due to the leaching with increase of recycling, and the aggregation of active metals.