Synergistic electronic transfer, π-π interactions, and wetting effects drive quinoline hydrogenation over in-situ N-doped carbon-encapsulated Co/SiO2 catalysts

Abstract

Catalytic hydrogenation, balancing efficiency, selectivity, and sustainability, is a cornerstone of chemical synthesis. However, cobalt catalysts, despite their reactivity, suffer from thermal instability at high temperatures. To address this challenge, we herein propose a facile strategy integrating adsorption, high-temperature calcination-reduction, and encapsulation: The silica rich in oxygen-containing functional groups is used to adsorb cobalt ions for synthesizing Co₃O₄/SiO₂, followed by pyrolysis of nitrogen-containing polymers to fabricate carbon-encapsulated Co/SiO₂@NC catalysts with strong metal-support interactions (SMSI). The catalyst features uniformly distributed cobalt nanoparticles (13 nm) embedded within a nitrogen-doped carbon layer, demonstrating high activity (apparent rate constant k_s = 0.013 m⁻² h⁻¹) and structural stability in quinoline hydrogenation. This low-cost approach opens a new avenue for the practical utilization of cobalt-based catalysts. The nitrogen-doped carbon materials not only serve as adsorption sites for quinoline but also stabilizes cobalt nanoparticles via pyridinic nitrogen on its surface with hydrophobic sites. The cobalt nanoparticles act as active sites for catalytic hydrogenation, while hydrogen dissociation is identified as the rate-determining step. Pyridinic nitrogen atoms on the Co/SiO₂@NC are electron-deficient, while cobalt nanoparticles are electron-rich. Kinetics show first-order dependence on H₂ and zero-order on quinoline, with enhanced hydrophobicity boosting activity. This work advances cobalt catalyst design through nanostructure control, optimized metal-support interactions, and efficient electron transfer, providing a blueprint for next-generation hydrogenation catalysts.