The Critical Impacts of Ligands on Heterogeneous Nanocatalysis: A Review

Abstract

Ligand utilization is a necessary and powerful technique for the colloidal synthesis of nanoparticles (NPs) with controllable sizes and regulated morphologies. For catalysis applications, it is commonly believed that surface ligands on metal NPs block the active catalytic sites and reduce the catalytic activity. Nevertheless, since 2010, an increasing number of research groups have demonstrated the unexpected benefits of ligands that improve catalytic activity and/or selectivity. These benefits can be ascribed to the construction of an inorganic−organic interface, through which a series of factors, such as steric, electronic, and solubility effects, can be utilized to produce favorable changes to the interfacial environment. Considering the tremendous number of developments in this emerging research field, it is necessary to compile a comprehensive and systematic overview of recent advances. In this Review, we summarize the critical impacts of ligands on heterogeneous nanocatalysis. First, we introduce the vital roles of ligands in colloid syntheses for controllable sizes and regulated shapes. Second, the detrimental effects of ligands for nanocatalysis are described on the basis of traditional views. Third, a series of strategies for ligand removal are reviewed and compared. Fourth, on the basis of research that has been conducted in the past decade, the three main beneficial ligand effects (steric, electronic, and solubility) on heterogeneous nanocatalysis are classified and discussed. For each effect, the possible corresponding beneficial mechanism is presented, and typical examples are provided. Recent advances regarding density functional theory (DFT) calculations and the regulation of ligand surface coverage have been dedicated to explaining the ligand-promotion mechanism in nanocatalysis and searching for optimal nanocatalysts. Fifth, the stabilities of cutting-edge ligand-capped nanocatalysts before and after catalytic reactions are discussed. Finally, we highlight the remaining challenges and propose future perspectives. Although much progress has been achieved, the impacts of ligands on the catalytic activities of nanocatalysts are multifaceted and still debatable. We hope this Review will deepen readers' understanding of the actual impacts ligands have on heterogeneous catalysis.

In Situ Ruthenium Catalyst Modification for the Conversion of Furfural to 1,2-Pentanediol

“…HDA, TMP, and TBA showed TOFs of 99 h −1 , 71 h −1 , and 66 h −1 , respectively, HDA increasing the TOF substantially, almost twice the one without any surface modifier (Table 1, entry 5 vs. entry 1). We attribute that to the increase in electron density of the Ru surface by the coordination of the amines to the metallic surface [30,31,34,35,37]. It is interesting to take into consideration that amines weakly coordinate to the surface of the metallic nanoparticles as shown experimentally and theoretically in previous works [31,46], and for that reason are in equilibrium with the solution.…”

“…In addition to the suppression of the acetal, the impact of ligands adsorbed in the metallic surface in this reaction was assessed. The investigation of the role of the ligands on heterogeneous catalysis is a crucial topic [30,34]. Nevertheless, as the ligands/stabilizers have an impact modulating the size, shape, chemical, and crystalline structure, among other parameters and properties of the metallic surfaces and nanoparticles [45], it is difficult to compare its exact role in catalysis.…”

“…Knowing that this transformation is sensitive to support effects [9,14,15] and our experience of tuning activity and selectivity in catalysed reactions by changing the adsorbates on the metallic surfaces [30][31][32][33], we have studied the effect of the in situ addition of organic ligands in order to examine their impact in the outcome of this chemical transformation. The modulation of the catalytic properties of heterogeneous catalysts using surface adsorbates is an important field in catalysis, yet it is in its infancy [34]. The adsorbates are key parameters to modulate a plethora of structural and reactivity parameters of metal surfaces, and in this sense, it is sometimes difficult to drive exact conclusions on the phenomenon, especially the effect on catalysis.…”

Preparation of Metal-Immobilized Methacrylate-Based Monolithic Columns for Flow-Through Cross-Coupling Reactions

“…The properties of both components are essential for the characteristics and application of the microreactor [ 24 ]. The ligand is crucial for the highly selective binding of the metal catalyst, and the polymeric support is essential to improve the mechanical strength, chemical stability, mass transfer, and reusability of the microreactor [ 25 , 26 , 27 , 28 ]. The use of organic polymer supports for the immobilization of ligands has been widely investigated.…”

Low content Ru-incorporated Pd nanowires for bifunctional electrocatalysis

“…[11][12][13] As part of these systems, catalysis and catalyst design in half-cell reactions, such as the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER), have attracted considerable attention and include fundamental and applied studies. [14][15][16][17][18] In this regard, efficient and affordable catalysts that can reduce the overpotential and energy consumption are of particular interest.…”