3D Ruthenium Nanoparticle Covalent Assemblies from Polymantane Ligands for Confined Catalysis

Abstract

The synthesis of metal nanoparticle (NP) assemblies stabilized by functional molecules is an important research topic in nanoscience, and the ability to control interparticle distances and positions in NP assemblies is one of the major challenges in designing and understanding functional nanostructures. Here, two series of functionalized adamantanes, bisadamantanes and diamantanes bearing carboxylic acid or amine functional groups have been used as building blocks to produce, via a straightforward method, networks of ruthenium NP. Both the nature of the ligand and the Ru/ligand ratio affect the interparticle distance in the assemblies. The use of 1,3-adamantanedicarboxylic acid allows the synthesis of 3D networks of 1.7-1.9 nm Ru NP presenting interparticle distance of 2.5-2.7 nm. The surface interaction between Ru NP and the ligands were investigated spectroscopically using a 13 C labeled ligand, as well as theoretically with Density Functional Theory (DFT) calculations. We found that Ru species formed during the NP assembly are able to partially decarbonylate carboxylic acid ligands at room temperature. Decarbonylation of a carboxylic acid at room temperature in the presence of dihydrogen usually occurs on catalysts at much higher temperature and pressure. This result reveals a very high reactivity of ruthenium species formed during network assembling. The Ru NP networks were found active catalysts for the selective hydrogenation of phenyl acetylene, reaching good selectivity towards styrene. Overall, we demonstrated that catalyst activity, selectivity, and NP network stability are significantly affected by Ru NP interparticle distance, and electronic ligand effects. As such, these materials constitute a unique set that should allow a better understanding of the complex surface chemistry in carbonsupported metal catalysts.

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.…”

“…Taking into consideration this previous result, we examine here the possibility of using Ru/PVP catalysts to directly transform furfural into 1,2-PeD. 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. Even so, it has been demonstrated in some works that organic ligands are able to change the outcome of catalysed reactions when compared to bare metallic surfaces, or increasing activity or favouring the synthesis of a selected product [31,[35][36][37]. Interesting enough, recently some works point out that basic ligands together with acidic metallic surfaces could form frustrated Lewis pairs (FLP), which will be responsible for the modulation of the reactivity of metallic surfaces [38][39][40].…”

Gases

“…This CO arises both from THF decomposition and from carboxylic acid decarbonylation. 68 The latter occurred at surprisingly low temperature (room temperature). Catalytic decarbonylation of carboxylic acids in the presence of dihydrogen usually occurs at much higher temperatures and pressures, suggesting an unanticipated high reactivity of undercoordinated Ru species that are formed during the decomposition of [Ru(COD)(COT)] in the presence of H2 and carboxylic acids.…”

Pt/TiO2 Catalyzed Hydrogenation of Benzoic Acid with Unprecedented High Activity

“…For example, BA hydrogenation to cyclohexanecarboxylic acid (CCA) is an important step in the production of nylon-6 in industry [4][5]. However, the need to overcome the high resonance energy of the electron de cient aromatic ring [6] and the catalyst "poison" by carboxyl group [7,8] make BA hydrogenation as one of the most challenging transformations. Harsh conditions (100~250 o C, 50~150 bar H 2 ) are typically required in order to obtain high BA conversion, which inevitably causes the decrease in selectivity due to the side reactions of decarboxylation and over hydrogenation [9,10].…”