A novel mesoporous Co-B amorphous alloy was synthesized by controlling the chemical reduction of Co2+ with BH4- in the presence of surfactant. During liquid-phase cinnamaldehyde hydrogenation, mesoporous Co-B exhibited higher activity and selectivity to cinnamyl alcohol compared with nonporous Co-B. This higher activity was attributed to its high surface area and mesopores, which facilitated diffusion and adsorption of reactants, whereas its better selectivity was ascribed to the uniform distribution of Co active sites and their connection via a porous network, which facilitated the competitive hydrogenation of C = O against C = C coexisting in the cinnamaldehyde molecule, because C = C adsorption was inhibited due to steric hindrance. (c) 2007 Published by Elsevier Inc.