Effects of phosphine ligand denticity on catalytic activity and durability of gold nanoparticles in the oxidation of benzyl alcohol

Abstract

A key challenge in developing metal nanoparticle (NP) catalysts is to overcome the trade-off between the catalytic activity and resistance to aggregation. In this study, we prepared monodisperse gold NPs (diameter = 2–3 nm) protected by phosphine ligands with different denticities: triphenylphosphine (TPP), 1,2-bis(diphenylphosphino)ethane (DPPE), and tris(2-(diphenylphosphino)ethyl)phosphine (TDEP). We then investigated how the ligand denticity affects the catalytic activity and durability in the aerobic oxidation of benzyl alcohol (BnOH). The AuNPs adsorbed on the Cs₂CO₃ powder, which is required for deprotonating BnOH, acted as heterogeneous catalysts in 1,2-dichloroethane at 60 °C. Of the three AuNP catalysts, the TDEP-protected AuNPs exhibited the greatest activity per exposed Au atoms and the longest lifetime. Conversely, the DPPE- and TPP-protected AuNPs exhibited poorer performance in terms of activity and durability, respectively. This work provides a rational ligand design strategy that balances the activity and durability of metal NPs.