The Role of Co(111) Facets in Oxygen-Doped Carbon-Supported Cobalt Nanoparticles by Electron Transfer for Selective Quinoline Hydrogenation.

Quinoline, a toxic and persistent N-heterocycle abundant in coking and pharmaceutical wastewater, threatens aquatic ecosystems and human health. Catalytic hydrogenation enables its removal and resource recovery, yet noble metal costs and catalyst deactivation hinder practical application. Herein, we report Co nanoparticles loaded in carbon layers derived from metal-organic frameworks (MOFs) pyrolyzed at 600-1000 °C as nonprecious catalysts for selective quinoline hydrogenation. Pyrolysis temperature precisely tuned particle size (12.21-95.98 nm), exposed Co facets, surface wettability, and functional groups on the carrier surface, collectively governing catalytic performance. The Co(111) facet intensity correlates positively with hydrogenation activity, while Co3O4(422) facets on Co nanoparticles further promote the reaction. The optimized CoC800 delivered 98.54% quinoline conversion to 1,2,3,4-tetrahydroquinoline (2.6 MPa H2, 200 °C, 3 h) with 100% selectivity. Charge transfer from cobalt to carbon renders the cobalt surface electron-deficient, enhancing H2 and quinoline adsorption. This work establishes a "structure-activity" relationship for designing MOF-derived catalysts toward nitrogen-heterocycle remediation.