Surface-Bound Ligands Modulate Chemoselectivity and Activity of a Bimetallic Nanoparticle Catalyst

“Naked”
metal nanoparticles (NPs) are thermodynamically
and kinetically unstable in solution. Ligands, surfactants, or polymers,
which adsorb at a particle’s surface, can be used to stabilize
NPs; however, such a mode of stabilization is undesirable for catalytic
applications because the adsorbates block the surface active sites.
The catalytic activity and the stability of NPs are usually inversely
correlated. Here, we describe an example of a bimetallic (PtFe) NP
catalyst stabilized by carboxylate surface ligands that bind preferentially
to one of the metals (Fe). NPs stabilized by fluorous ligands were
found to be remarkably competent in catalyzing the hydrogenation of
cinnamaldehyde; NPs stabilized by hydrocarbon ligands were significantly
less active. The chain length of the fluorous ligands played a key
role in determining the chemoselectivity of the FePt NP catalysts.