The ability to resemble metalloenzymes and to bridge between homogeneous and heterogeneous catalysis makes single-atom catalysts (SACs) promising for heterogeneous organic synthesis. Herein, we report the fitting of atomically isolated Ni (Ni SACs) on a nitrogen-rich (N-rich) covalent organic framework-templated carbon (Ni@N-CTC), which exhibits remarkable catalytic activity in the Buchwald–Hartwig N-arylation reaction. The demonstrated impressive catalytic activity of Ni@N-CTC is attributed to the trapping of the Ni SACs inside the N-rich nanoporous carbon matrix, which provides surplus catalytic active sites as it prevents agglomeration of Ni to form nanoparticles and ensures the preservation of the catalytically active coordinatively unsaturated nickel–nitrogen (Ni–N) sites originating from the exotic metal–support coordination and electronic interactions which were confirmed by X-ray absorption spectroscopy (XAS) analysis and computational studies.