Phenanthroline-functionalized graphene as a ligand platform for single-atom catalysis

The precise anchoring of single metal atoms on solid supports remains a key challenge in the design of single-atom catalysts (SACs), particularly for carbon-based materials where metal coordination environments are often poorly defined. We report a graphene-based support covalently functionalized with 1,10-phenanthroline-5amine groups via nucleophilic substitution on fluorographene in DMSO. This approach introduces well-defined chelating sites that enable the rational and selective immobilization of transition metals. A copper-based SAC was synthesized by impregnating the functionalized graphene with a CuCl2 solution. Spectroscopic and microscopic analyses confirmed the formation of atomically dispersed Cu(I) species coordinated by phenanthroline ligands, with no detectable nanoparticle formation. The resulting catalyst exhibited high activity in the Chan–Lam coupling of 1H-imidazole with phenylboronic acid, achieving a turnover frequency of 3.8 h 1, and outperformed heterogeneous benchmark systems, including commercial CuO nanoparticles. However, recyclability tests revealed a decline in catalytic activity after four cycles, primarily due to the leaching of Cu-phenanthroline complexes. These findings demonstrate the potential of functionalized graphene as a platform for developing SACs with well-defined coordination environments. Nevertheless, enhancing catalyst stability, e.g., through secondary anchoring strategies, optimized metalation protocols, or post-synthetic stabilization, is needed for future industrial applications.