Ultrasmall Platinum Stabilized on Triphenylphosphine-Modified Silica for Chemoselective Hydrogenation

Chemoselective hydrogenation of substrates with more than one functional group that could be hydrogenated is quite challenging and is of fundamental importance. Here, the enhanced chemoselectivity of ultrasmall (<1 nm) platinum nanoparticles (NPs) stabilized on silica modified with triphenylphosphine (PSiO2) in hydrogenation reactions is reported. Platinum NPs on PSiO2 exhibit much higher selectivity than those on SiO2 in the hydrogenation of acetophenone to 1-phenylethanol (99.9 versus 36 %) and hydrogenation of phenylacetylene to styrene (85 versus 52 %). The results of NMR spectroscopy, X-ray photoelectron spectroscopy, and in situ CO adsorption FTIR spectroscopy indicate the existence of strong interactions between triphenylphosphine and Pt NPs. Consequently, Pt NPs on PSiO2 have smaller particle sizes and more positive Pt 4 f binding energy than those of Pt/SiO2; these are the main contributors to the superior chemoselectivity of Pt NPs. The organically modified silica could act as an efficient solid ligand for tuning the catalytic performance of metal NPs.