Co⁰/O_v-Co Synergy in Co–Al Metal–Metal Oxide Catalysts by Atomic Ratio Control for the Efficient Fatty Acid Hydrogenation to Fatty Alcohol

Selective hydrogenation of carboxylic acids to alcohols remains a challenge due to the requirement of synergistic multiple active sites for H₂activation, reactant adsorption, and selective C–O bond scission. Here, we construct a series of Co–Al metal–metal oxide (MMO) catalysts via the hydrogen-induced reduction of layered double hydroxide (LDH) precursors with tunable Co/Al ratios. The optimal Co₄Al₁-MMO catalyst exhibits highly dispersed Co⁰nanoparticles alongside abundant oxygen vacancies (O_v-Co). The Co⁰/O_v-Co dual sites synergistically promote H₂dissociation and carbonyl oxygen C=O bond activation, while moderate lattice oxygen stabilizes the metastable structure. Under mild conditions (180 °C, 2 MPa of H₂, 3 h), the catalyst achieves 100% conversion of octanoic acid with 99% alcohol selectivity, outperforming state-of-the-art noble-metal systems. This work provides a general strategy for engineering cooperative metallic/defective sites in nonprecious MMO catalysts for selective hydrogenation reactions.