Supported, Ligand-Functionalized Nanoparticles: An Attempt to Rationalize the Application and Potential of Ligands in Heterogeneous Catalysis

The binding of molecules to the surface of nanoparticles (NPs) for the use as ligands to manipulate the catalytic properties of NPs is an emerging research area. Various studies with interesting results have been reported in the past few years, but it seems not clear how these findings could be merged into some kind of unified picture, describing the mechanism of action of ligands in heterogeneous catalysis. The aim of this article is to summarize some of the recent achievements in this field with focus on discussing these results using concepts from heterogeneous and homogeneous catalysis. By this it is attempted to separate the influence of ligands into (i) changing the surface properties and (ii) acting as a function above or perpendicular to the surface. The first aspect can be rationalized by the knowledge from bimetallic catalysis. In contrast, the second proposes the relevance of ligand-reactant interactions, as known from homogeneous catalysis, in order to manipulate adsorption, activation, and conversion of reactants. As the application of ligands in heterogeneous catalysis is still a young research field and the full potential of the approach still unknown, this article does not claim to give a complete summery of all results gained within this field. Instead, the author aims to present a picture that may give some guidance for future studies in this area, based on established knowledge from homo-and heterogeneous catalysis.