Facile benzene reduction promoted by a synergistically coupled Cu–Co–Ce ternary mixed oxide

Abstract

Hydrogenation of aromatic rings promoted by earth-abundant metal composites under mild conditions is an attractive and challenging subject in the long term. In this work, a simple active site creation and stabilization strategy was employed to obtain a Cu⁺-containing ternary mixed oxide catalyst. Simply by pre-treatment of the ternary metal oxide precursor under a H₂ atmosphere, a Cu⁺-derived heterogeneous catalyst was obtained and denoted as Cu₁Co₅Ce₅O_x. The catalyst showed (1) high Cu⁺ species content, (2) a uniform distribution of Cu⁺ doped into the lattices of CoO_x and CeO₂, (3) formation of CoO_x/CuO_x and CeO₂/CuO_x interfaces, and (4) a mesoporous structure. These unique properties of Cu₁Co₅Ce₅O_x endow it with pretty high hydrogenation activity for aromatic rings under mild conditions (100 °C with 5 bar H₂), which is much higher than that of the corresponding binary counterparts and even exceeds the performance of commercial noble metal catalysts (e.g. Pd/C). The synergetic effect plays a crucial role in the catalytic procedure with CeO₂ functioning as a hydrogen dissociation and transfer medium, Cu⁺ hydrogenating the benzene ring and CoO_x stabilizing the unstable Cu⁺ species. This will unlock a new opportunity to design highly efficient earth-abundant metal-derived heterogeneous catalysts via interface interactions.