(475g) Coordination-Mediated Atomic Metal Catalysts for Cascaded Transformation of ?-O-4 Dimeric Model Compound into Quinoline

The valorization of lignin and derived fragments is still challengeable to date because of the undesired performance of catalysts, high cost and complicity of the reaction processes. Here, we report the fabrication of atomic-metal catalysts for the facile cascaded transformation of lignin β-O-4 dimeric model compound into quinoline. A series of dual-metal single-atom (SA) moieties (i.e., MaC₄ and Mb₂N₆) are integrated on N-doped carbons with designed compositions and coordination configurations. Characterizations indicate the homogeneous distribution of uniform and modifiable metal SA sites, over which the electron distribution is significantly polarized due to the synergistic interactions. The distinctive physicochemical properties of catalysts afford attractive performances in the cascaded synthesis of quinoline from lignin β-O-4 dimeric model compound through C‒O bond cleavage, alcohol oxidation, oxidative-coupling, and nitrogen-heterocyclic ring construction. In a continuous flow instrument, the CuC₄/Co₂N₆@NC catalyst furnishes 93.7% yield of 2-phenylquinoline with a space time yield (STY) of 75.7 g·g_cat·h^−1. The control experiments and density functional theory (DFT) calculations reveal that CuC₄ could regulate the electronic property of the adjacent Co₂N₆, endowing the latter with high efficiency in selective C‒O bond cleavage, C‒C coupling and O₂ activation in the cascaded transformation.