Structural Control and Catalytic Reactivity of Peptide-Templated Pd and Pt Nanomaterials for Olefin Hydrogenation

Abstract

Diverse classes of metallic nanostructures have been explored recently for a variety of applications, including energy efficient catalytic transformations. The morphology, size, and local chemical environment of the catalytic nanomaterials can have dramatic effects on their reactivity. Herein, we demonstrate a peptide-template-based approach for the synthesis of Pd and Pt nanostructures of varying morphologies under ambient conditions. In this report, we examine the effect of the metal/peptide ratio over an expansive range to demonstrate the stepwise production of materials ranging from nanospheres to nanoparticle networks for the Pd structures. Interestingly, when the metallic composition was changed to Pt, only spherical materials were generated, indicating that the metallic composition of the nanostructures plays a key role in the final morphology. The hydrogenation of allyl alcohol was then employed as a model reaction to examine the catalytic reactivity of these metallic nanomaterials. Under environmentally benign reaction conditions, high turnover frequency values were observed for the metallic Pd and Pt nanocatalysts that was independent of the material morphology. Given their high degree of reactivity and facile synthetic preparation, these materials could prove to be versatile and efficient catalysts for a variety of industrially and environmentally important reactions.

Effects of Noncovalent Interactions on the Catalytic Activity of Unsupported Colloidal Palladium Nanoparticles Stabilized with Thiolate Ligands

“…The adsorption of alkene group instead of −OH group is also known to be a favorable mode of adsorption for allylic alcohols on Pd surface. 39–41 …”

Peptide-templated noble metal catalysts: syntheses and applications

“…78,79 They found that by varying Pd/peptide ratios from 60 to 120, the shapes of Pd catalysts changed from spherical (Pd/peptide ratios = 60–80), linear/ribbon-like (90–110) to NPN (110–120) structure, but the size of these different Pd nanostructures was still constrictively controlled. 38,78 Owing to the unique ability to load selective amounts of Pd materials into the scaffolds, both the metallic surface area and the penetration depth of reagents to the Pd surface can be flexibly altered. Therefore, these R5-templated Pd catalysts were proven to be highly active in the Stille coupling reaction, the 4-nitrophenol reduction reaction, and the hydrogenation of allyl alcohol, just like the Pd4-templated Pd catalysts.…”

“…Therefore, these R5-templated Pd catalysts were proven to be highly active in the Stille coupling reaction, the 4-nitrophenol reduction reaction, and the hydrogenation of allyl alcohol, just like the Pd4-templated Pd catalysts. 38,78 On the other hand, the surface areas and the penetration depth for oxidative addition differ for Pd NPs of different shapes, thus leading to changes in their catalytic properties. 38 For spherical Pd catalyst, there exist the highest Pd surface and the largest penetration depth as a result of the high dispersity of Pd NPs.…”

Hydrogenation of allyl alcohols catalyzed by aqueous palladium and platinum nanoparticles

“…[17][18][19][20] The selectivity in the reduction of the C=C group in the presence of other functional substituents (e.g., C=O or OH), can be controlled by a variety of parameters, such as the nature of the metal catalyst, the presence of a second metal (bimetallic catalysts), the size of metal particles and the nature of the supporting materials (electron-donating or -withdrawing ligand effects, metal-support interactions and solvent effect). [29][30][31][32][33][34][35] However, the preparation of metal NPs often involves the use of environmental unfriendly organic solvents. 27,28 In particular, some Palladium and Platinum NPs are reported to be active catalysts in the hydrogenation of unsaturated hydrocarbons or allyl alcohols.…”