On-Surface Hierarchical Synthesis of Nitrogen-Doped Covalent Networks on Au(111)

On-surface synthesis has garnered significant attention for enabling atomically precise fabrication of low-dimensional covalent nanostructures. While substantial progress has been achieved in synthesizing one-dimensional (1D) covalent chains, the construction of two-dimensional (2D) covalent architectures based on a hierarchical strategy has been less reported due to the complexity. Herein, by combining scanning tunneling microscopy (STM) and density functional theory (DFT) calculations, we visualize the hierarchical synthesis of a 2D nitrogen-doped covalent network on Au(111) through sequential dehalogenative and dehydrogenative coupling reactions. Moreover, we reveal that nitrogen doping in the precursor substantially reduces the energy barrier for dehydrogenation. These results establish the critical advantage of nitrogen-doped precursors in steering on-surface reactions toward 2D covalent frameworks, providing fundamental insights for the rational design of precursors to achieve targeted covalent nanostructures.