Constructing Co@C nanoparticles with chainmail-structure for highly efficient hydroformylation of 1-hexene

Constructing highly active noble-metal-free heterogeneous catalysts is the crux for the hydroformylation of long-chain α-olefins. Herein, novel chainmail-structured cobalt oxide nanoparticles (CoO@C|SBA-15) are fabricated by the channel confinement strategy, which display excellent activity for the 1-hexene hydroformylation. Specifically, the obtained catalyst shows 100% 1-hexene conversion and 94% heptanal selectivity, as well as up to 2.0 linear to branch (l/b) ratio, outperforming most of heterogeneous noble metal catalysts. Remarkably, in-situ DRIFT spectra combined with density functional theory calculations disclosed the metallic Co derived from in-situ reconstruction of CoO is the key active site for 1-hexene hydroformylation. Specifically, the reconstructed Co site is responsible for the adsorption of 1-hexene, and the graphite carbon layer promotes the adsorption of H2 and CO by interacting with the reconstructed Co. Moreover, the graphite carbon layer provides a strong protective effect on the internal cobalt active sites and thus enhances the catalytic stability during the harsh condition. This work provides a new method for designing the low-cost heterogeneous catalyst and emphasizes the intrinsic active sites for 1-hexene hydroformylation reaction.