Pd Single Atoms on N-Doped Hollow Carbon Nanosheet Assemblies for Suzuki Cross-Coupling Reactions of Aryl Chlorides

Palladium-catalyzed Suzuki-Miyaura cross-coupling reaction is a powerful route to construct carbon-carbon bonds in fine-chemical synthesis. However, the activation of relatively chemically inert aryl chlorides under mild conditions in this reaction is still a great challenge. Herein, N-doped hollow carbon nanosheet assemblies (HCNAs) were first developed by hydrothermal carbonization of glucose through an in situ self-generating template method, and the corresponding Pd single-atom catalyst (Pd₁/HCNAs) fabricated by a conventional deposition-precipitation method showed superior catalytic activity (TOFs = 499 h^-1) and high stability for the Suzuki coupling reaction of chlorobenzene under mild condition. Characterizations of transmission electron microscopy, electron paramagnetic resonance spectroscopy, Raman spectra, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy showed that the high catalytic activity and stability of Pd₁/HCNAs were related with its full positively charged Pd single-atom active sites and the low reducibility of Pd atom due to the strong interaction between Pd atom and the HCNA carrier. Meanwhile, the relative high chlorobenzene and phenylboric acid adsorption and the low affinity to product biphenyl as well as the special three-dimensional structure of Pd₁/HCNAs were also beneficial to improve the catalytic activity.