Thiophene Modification of the Pt/SOD Catalyst to Enhance Catalytic Selectivity in Hydrogenation Reactions

Rationally controlling the adsorption conformation of reactants onto metal nanoparticles to promote catalytic selectivity is still a grand challenge. Herein, compared to the unprotected sodalite (SOD) zeolite-supported platinum nanoparticles (Pt/SOD), the introduction of organic thiophene onto Pt/SOD as the composite catalyst (Pt/SOD-thiophene), in the reaction of hydrogenation of p-chloronitrobenzene to p-chloroaniline, exhibited excellent catalytic selectivity and high yield as well as good reusability. Based on the control experiments combined with density functional theory calculations, this superior selectivity of Pt/SOD-thiophene was attributed to the proper occupation of the surface of Pt nanoparticles by adsorption of thiophene to sterically constrain the nitroarene adsorption on Pt nanoparticles via the end-on adsorption geometry, rather than the thermodynamically favorable flat-lying geometry. Such interesting end-on adsorption geometry made either the end of nitro group adsorption onto the Pt surface or the end of C–Cl group adsorption, as a result of the much lower apparent activation energy of hydrogenation of end-on adsorbed nitro group over the Pt/SOD-thiophene catalyst than that of the C–Cl group, thus showing outstanding catalytic selectivity.