Improving Catalytic Hydrogenation Performance of Pd Nanoparticles by Electronic Modulation Using Phosphine Ligands

Abstract

Tuning the activity and selectivity of metal nanoparticles (NPs) is a long-term pursuit in the field of catalysis. Herein, we report successfully improving both the activity and chemoselectivity of Pd NPs (1.1 nm) with triphenylphosphine (PPh3) cross-linked in the nanopore of FDU-12. The electron-donating effect of PPh3 increases the surface electronic density of Pd NPs and weakens the Pd–H bond, as evidenced by the results of XPS, in situ FT-IR adsorption of CO, and H2–D2 exchange reactions. Consequently, Pd NPs modified with PPh3 obtain >99% selectivity to 1-phenylethanol in acetophenone hydrogenation and 94% selectivity to styrene in phenylacetylene hydrogenation. Furthermore, the activity of Pd NPs is enhanced and suppressed by PPh3, respectively, in the hydrogenation of electrophilic nitro compounds and nucleophilic carbonyl substrates. Our primary results shed some light on judiciously choosing organic ligands for modifying the catalytic performance of metal NPs toward specific chemical transformations.

Study of the effect of the ligand structure on the catalytic activity of Pd@ ligand decorated halloysite: Combination of experimental and computational studies

“…In the following, to study the merit of the developed protocol, the efficiency of Pd@Hal/di‐urea for the hydrogenation of nitrobenzene was compared with that of some previously reported Pd‐based catalysts, Table . It is worth noting that to date, various efficient methods and catalysts have been developed for this reaction . Each of the methods benefited from some merits and suffered from some drawbacks.…”

Rh Catalyzed Selective Hydrogenation of Nitroarenes under Mild Conditions: Understanding the Functional Groups Attached to the Nanoparticles

“…It is clear that Fe 3 O 4 @SiO 2 −NH 2 −RhNPs and Fe 3 O 4 @SiO 2 −N=CH 2 −RhNPs exhibit excellent selectivity. Thus, we can conclude that the catalysts with higher Rh 0 /Rh 3+ ratios have better selectivity for reduction of nitro‐groups . To understand the effect of different functional groups on catalysts, field inductive parameter (F), which is used to describe the electronic inductive effect, was introduced and presented in Table .…”

“…Thus, we can conclude that the catalysts with higher Rh 0 /Rh 3 + ratios have better selectivity for reduction of nitro-groups. [21,33] To understand the effect of different functional groups on catalysts, field inductive parameter (F), which is used to describe the electronic inductive effect, [34] was introduced and presented in Table 3. With the enhancement of F, the group's electron cloud density decreases then results the lower Rh 0 /Rh 3 + ratios, which lead to the lower selectivity.…”

“…Triphenylphosphine is verified positive for Pd-based hydrogenation catalyst, both on enhancing surface electron density and splitting PdÀ H bonds. [21] It was also reported that the electron density of ultrathin platinum nanowires can be promoted by ethylenediamine coating. This favors the adsorption of electron-deficient reactants over electron-rich products, then the selectivity could be effectively improved.…”

“…By doping with oxygen and nitrogen into carbon nanotubes, the catalysts were increased by two and four times, respectively. Triphenylphosphine is verified positive for Pd‐based hydrogenation catalyst, both on enhancing surface electron density and splitting Pd−H bonds . It was also reported that the electron density of ultrathin platinum nanowires can be promoted by ethylenediamine coating.…”