Comparative Catalytic Properties of Supported and Encapsulated Gold Nanoparticles in Homocoupling Reactions

Abstract

This report describes strategies to increase the reactive surfaces of integrated gold nanoparticles (AuNPs) by employing two different types of host materials that do not possess strong electrostatic and/or covalent interactive forces. These composite particles are then utilized as highly reactive and recyclable quasi-homogeneous catalysts in a CC bond forming reaction. The use of mesoporous TiO 2 and poly(N-isopropylacrylamide), PNIPAM, particles allows for the formation of relatively small and large guest AuNPs and provides the greatly improved stability of the resulting composite particles. As these AuNPs are physically incorporated into the mesoporous TiO 2 (i.e., supported AuNPs) and PNIPAM particles (i.e., encapsulated AuNPs), their surfaces are maximized to serve as highly reactive catalytic sites. Given their increased physicochemical properties (e.g., stability, dispersity, and surface area), these composite particles exhibit notably high catalytic activity, selectivity, and recyclability in the homocoupling of phenylboronic acid in water and EtOH. Although the small supported AuNPs display slightly faster reaction rates than the large encapsulated AuNPs, the apparent activation energies (E a) of both composite particles are comparable, implying no obvious correlation with the size of guest AuNPs under the reaction conditions. Investigating the overall physical properties of various composite particles and their catalytic functions, including the reactivity, selectivity, and E a , can lead to the development of highly practical quasi-homogeneous catalysts in green reaction conditions.

Synergistic Bonding of Poly(N-isopropylacrylamide)-Based Hybrid Microgels and Gold Nanoparticles Used for Temperature-Responsive Controllable Catalysis of p-Nitrophenol Reduction

“…Comparing AuNPs@MG-OH and AuNPs@MG-SH, AuNPs@MG-SH self-assembled by electrostatic interaction and Au−S bonding has better stability to facilitate the reduction smoothly, further improving the catalysis efficiency than that of AuNPs@MG-OH. 11,32,63,76,77 Competitiveness against Known PNIPAM-Based Materials. The catalytic performance of the AuNPs@MG-SH hybrid microgels (surface-covered) prepared in this study was compared with that of similar works according to the halflife (t 1/2 ), the mole ratio of Au and 4-NP, and the conversion of 4-NP.…”

Sonochemical preparation of polymer–metal nanocomposites with catalytic and plasmonic properties

“…2b). 9,42 For polymer-Au nanocomposite (Fig. 2a), only a very small amount of PVP was added, and the AuNPs were embedded on the hydrophilic block of polymeric nano-spheres, leaving the relatively larger area of "naked" Au surface thus more accessible active sites.…”

“…citrate) in conventional metal nanoparticles often act as a physical barrier, which blocks the access of reactants during the reaction and adversely affects the overall catalytic performance. 8,9 By replacing the stabilizing/capping agents with polymeric nanoparticles, the surface of the metal nanoparticles is free from any capping agent barrier, thus it can serve as highly active catalysts. For polymer-metal nanocomposite, the metal nanoparticles are usually prepared in situ by reduction of a metal salt and immobilized on polymer based on the interaction between one of the polymer blocks and the metal ion.…”

Recent Progress of Metal Nanoparticle Catalysts for C–C Bond Forming Reactions

“…Bae, Byun, and Kim et al prepared small and large Au NPs stabilized in mesoporous TiO 2 and poly(N-isopropylacrylamide) particles, respectively. These Au NPs exhibited a notably high catalytic activity in the homocoupling of phenylboronic acid, and interestingly, there was no obvious correlation between the apparent E a values and the size of Au NPs [160]. Dewan et al reported the first synthesis of a renewable, recyclable, environmental benign bio-nanocellulose-based honeycomb-like heterogeneous surface from waste pomegranate peel.…”