Selective hydrogenation of cinnamaldehyde catalyzed by Co-doped Pt clusters: a density functional theoretical study

Using Pt-6 clusters as model catalysts in this paper, by means of the B3LYP functional in DFT at the 6-31+G(d) level (the LanL2DZ extra basis set was used for Pt atoms) we studied separately the microreaction mechanism of the selective hydrogenation of cinnamaldehyde catalyzed by pure Pt clusters and co-doped Pt clusters. The rationality of the transition state can be proved by vibration frequency analysis and IRC computations. Moreover, atoms-in-molecules (AIM) theory and natural bond orbital (NBO) theory were applied for discussing the interaction among orbitals and the bonding characteristics. The calculating results indicate that Pt-6 clusters are favored for catalyzing the activation and hydrogenation of the C=O bond in cinnamaldehyde molecules, eventually producing cinnamyl alcohol, which proved that Pt-6 clusters have a strong reaction selectivity for catalyzing the hydrogenation of cinnamaldehyde. Compared with Co-doped Pt clusters, Pt-6 clusters are more likely to catalyze the activation and hydrogenation of the C=O bond. Using Co-doped Pt clusters to catalyze the selective hydrogenation reaction of cinnamaldehyde to produce cinnamyl alcohol, the activation energy is lower than that of the reaction catalyzed by pure Pt clusters. The doped catalyst has a synergetic catalytic effect. Our findings have explained the mechanism of action of the doped catalyst and the experimental phenomena.