Charge State of Au₂₅(SG)₁₈ Nanoclusters Induced by Interaction with a Metal Organic Framework Support and Its Effect on Catalytic Performance

Abstract

We investigated the charge transfer between Au25(SG)18 nanoclusters and metal–organic framework (MOF) supports including Mil-101-Cr, Mil-125-Ti, and ZIF-8 by an X-ray photoemission technique and discussed the influence of resulted charge states of supported Au25(SG)18 nanoclusters on the 4-nitrophenol reduction reaction. Charge transfer from Au25(SG)18 to Mil-101-Cr induces positive charge Auδ+ (0 < δ < 1) while charge transfer from ZIF-8 to Au25(SG)18 generates negative charge Auδ− due to different metal–support interactions. Au25(SG)18 on Mil-125 shows metallic Au0, similar to unsupported Au25(SG)18, due to negligible charge transfer. The resulted charge state of Auδ− inhibits the formation of adsorbed hydride (H–) species because of electrostatic repulsion, while Auδ+ impairs the reductive ability of adsorbed hydride (H–) species due to strong affinity between them. In comparison, metallic Au0 in Au25(SG)18/Mil-125 and unsupported Au25(SG)18 presents the optimum catalytic activity. The current work provides guidelines to design effective metal nanoclusters in heterogeneous catalysis through metal–support interaction exerted by metal-oxo/nitric clusters within MOFs.

Exploiting the Fracture in Metal‐Organic Frameworks: A General Strategy for Bifunctional Atom‐Precise Nanocluster/ZIF‐8(300 °C) Composites

“…The analysis of the changes of Ag3d, Zn2p, S2p, and N1s shows that charge transfer occurred from Au 12 Ag 32 NCs to ZIF‐8(300 °C). [ 20 ] Surprisingly, no charge transfer was observed between Au 12 Ag 32 NCs and untreated ZIF‐8 in Au 12 Ag 32 @ZIF‐8 composite. The same phenomenon was found in Au 46 Ag 24 /ZIF‐8(300 °C) composite, where the binding energy of Zn 2p 3/2 with a 0.62 eV shift and the binding energy of Ag 3d 5/2 with a 0.21 eV shift (Figure 1C,E).…”

Surface-Clean Au25 Nanoclusters in Modulated Microenvironment Enabled by Metal–Organic Frameworks for Enhanced Catalysis

“…It is possible to remove surface ligands from metal NCs encapsulated in MOFs, , generating ligand-free metal NCs stabilized in MOF pores. To date, although there have been several reports on the incorporation of metal NCs into MOFs in recent years, − the studies are simply limited to the function synergy between the two components, and the MOF contribution to the resulting catalytic performance has not been fully exploited. In fact, the MOF pore walls can be readily furnished with diverse functional groups, creating a modulated microenvironment around the encapsulated metal NCs.…”

Metal–support interactions for heterogeneous catalysis: mechanisms, characterization techniques and applications

“…Chu et al prepared a supported Au 25 (SG) 18 catalyst by the associate degree equal volume impregnation methodology. 95 The charge transfer from Au 25 (SG) 18 96 This methodology can be employed for regulating the interaction between metallic elements and the corundum support. Also, low angles allow the metallic element to interact with the substrate more effectively, resulting in a reduction in sintering under harsh reaction conditions.…”