Insight into chemoselectivity of nitroarene hydrogenation: A DFT-D3 study of nitroarene adsorption on metal surfaces under the realistic reaction conditions

Abstract

The adsorption of nitrobenzene and 4-nitrostyrene on the Pt(111) and the Au(111) surfaces under the general reaction condition of nitroarene catalytic hydrogenation is investigated utilizing periodic density functional theory calculations with the Grimme’s empirical three-body dispersion correction to understand the influence of adsorption configurations on chemoselectivity of nitroarene compound hydrogenation. It is found that at the low coverage both nitrobenzene and 4-nitrostyrene tend to adsorb paralleling to the Pt(111) and the Au(111) surfaces. Based on the crystal orbital Hamilton population analysis, it is found that the chemical bonding between nitro group and Pt(111) surface is weak. The adsorption configurations of nitrobenzene and 4-nitrostyrene are determined by the chemisorption strength of phenyl group and vinyl group. Under the reaction condition, the 1/9 ML nitrobenzene and 4/9 ML hydrogen atom can be coadsorbed while the 1/6 ML 4-nitrostyrene and 1/3 ML hydrogen atom can be coadsorbed on Pt(111). With the increase of the coverage, nitrobenzene still remains its paralleled adsorption configuration while the adsorption configuration of 4-nitrostyrene is switched to the tilted adsorption configuration through vinyl group without the chemisorption of phenyl and nitro group on Pt(111). In addition, the competitive adsorption with hydrogen will not change the adsorption configuration of nitrobenzene and 4-nitrostyrene under the reaction condition. On Au(111), the physical adsorption strength determines the adsorption configuration. The paralleled adsorption with the shortest average distance between the adsorbate and Au(111) surface is preferred. At the paralleled adsorption configuration, the chemoselectivities of the hydrogenation on these functional groups are similar if only in terms of geometric configuration. However, the hydrogenation on nitro group encounters the problem of steric hindrance at the tilted adsorption configuration through vinyl group, which makes it unfavorable. Therefore, the catalysts which could form strong chemical bonding with nitro group, leading to the preferential vertical adsorption configuration via nitro group, are expected for the high selectivity towards nitro group hydrogenation.