Catalytic Reduction by Quasi‐Homogeneous Gold Nanoclusters in the Liquid Phase

Abstract

Reduction reactions play significant roles in industrial manufacture, and supported metal nanoparticles (NPs) show great prospect for mass production. The gold NPs have achieved expanding progress in selective reduction in recent years and will lead to a hot issue in the future. However, the designing of efficient catalysts is currently quite challenging because of the lack of systematic understandings on the fundamentals of the catalytic efficiency. Fortunately, tremendous advances can be expected with the aid of quasi‐homogeneous NPs. This review highlights the unsupported gold NPs or nanoclusters (NCs) catalyzed reduction reactions, which include single‐electron‐transfer catalysis, selective hydrogenation of carbonyl and nitro groups. The tentative catalytic mechanism and the size‐dependence of gold nanocatalyst have also been discussed in this review.

Tuning the Accessibility and Activity of Au25(SR)18 Nanocluster Catalysts through Ligand Engineering

“…Gold has become a significant focus for research in catalysis since its remarkable catalytic properties were discovered by Haruta et al. in 1989 . Recently, the catalysis community has witnessed remarkable advancements in the development of Au‐based catalysts, typically for Au particles at nanometer or even sub‐nanometer size range .…”

“…In particular, Au 25 (SR) 18 consists of a Au 13 icosahedral core, capped by six ‐SR‐Au‐SR‐Au‐SR‐ motifs . A proper control of the ligand shell of Au 25 (SR) 18 might facilitate the understanding of the catalytic mechanism of nanogold catalysts and ultimately contribute to the rational design of highly active and selective Au NC catalysts . In this study, we chose 4‐nitrophenol hydrogenation (using excess NaBH 4 as the hydrogen source) as a model catalytic reaction due to its simplicity and well‐established characterization protocol.…”

“…Gold has become as ignificant focusf or research in catalysis since its remarkable catalytic properties were discovered by Haruta et al in 1989. [16] Recently,t he catalysisc ommunity has witnessed remarkable advancements in the development of Au-based catalysts, typically for Au particlesa tn anometero r even sub-nanometer size range. [17,18] In particular, ultrasmall Au NCs with core size below 2nmh ave receivedi ncreasing interest in the field, largely due to their well-definedm olecular size/structure and some intriguing molecular-like properties, such as quantized charging and HOMO-LUMOe lectronic transition (distinctly different from their larger counterparts, i.e.,Au nanoparticles typicallya bove 2nm).…”

“…[19] Ap roper control of the ligand shell of Au 25 (SR) 18 might facilitate the understanding of the catalytic mechanism of nanogold catalystsa nd ultimately contribute to the rational design of highly active and selectiveA uN Cc atalysts. [16,31] In this study,w ec hose 4-nitrophenol hydrogenation (using excess NaBH 4 as the hydrogen source)a sam odel catalytic reactiond ue to its simplicity and well-established characterization protocol. As the reactioni si na queouss olution, we would like to focus our investigation on those hydrophilic thiolate ligands.…”

“…To the best of our knowledge,t his is the first attempt utilizing the atomically precise Au 25 (SR) 18 NCs to identify the role of chain length and functional groups of hydrophilic thiolatel igands to the catalytic activity anda ccessibility of the catalysts in aqueous solution. [16] As ap roof-of-concept, we first preparedh ighp urity Au 25 (SR) 18 NCs protected by different ligands. Three groups of Au 25 (SR) 18 NCs of different ligands were synthesized.…”