Microenvironment Engineering of Ruthenium Nanoparticles Incorporated into Silica Nanoreactors for Enhanced Hydrogenations

Abstract

It is a challenging task to promote the activity and selectivity of a catalyst via precisely engineering the microenvironment, an important factor related with the catalytic performance of natural catalysts. Motivated by the water effect in promoting the catalytic activity explored in this work, a nanoreactor modified with phosphine ligand enabled the efficient hydrogenation of benzoic acid (BA) over Ru nanoparticles (NPs) in organic solvent under mild conditions, which cannot be achieved in unmodified nanoreactors. Both density functional theory (DFT) calculations and catalytic performance tests showed that the phosphine ligands can manipulate the adsorption strength of BA on Ru NPs by tuning the surface properties as well as preferentially interacting with the carboxyl of BA. The insights obtained in the present study provide a novel concept of nanoreactor design by anchoring ligands near catalytically active centers.

Highly efficient and selective aqueous phase hydrogenation of aryl ketones, aldehydes, furfural and levulinic acid and its ethyl ester catalyzed by phosphine oxide-decorated polymer immobilized ionic liquid-stabilized ruthenium nanoparticles

“…However, the presence of a single broad signal at ca. δ 27 ppm in the solid state 31 P NMR spectra of the products provided the first indication that they were the corresponding phosphine oxide-based PIIL-stabilized RuNPs, 2a and 2a.PEG (Fig. 1), as there was no evidence for free phosphine at δ −6.8 ppm in the 31 P NMR spectrum.…”

“…30 Most recently, ruthenium nanoparticles incorporated into phosphine-modified nanoreactors catalyze the hydrogenation of benzoic acid whereas the corresponding unmodified nanoreactor was completely inactive; the efficacy of the phosphine-modified system was attributed to preferential absorption of the benzoic acid on the electron-rich RuNP surface. 31 However, ligand effects are not restricted to phosphine-based donors as amines have also been shown to modify the performance of Pt, Pd and Ru nanoparticles as catalysts for the hydrogenation of carbonyl compounds and nitroarenes by modifying surface electronic structure and/or steric properties. 32 We have recently been exploring the concept of heteroatom donor-modified polymer immobilized ionic liquid-stabilized nanoparticles (MNP@HAD-PIILS) on the basis that covalent attachment of an ionic liquid to a polymer would combine the well-documented advantages of ionic liquids such as catalyst stabilization, facile catalyst activation and enhancements in rate and/or selectivity with those of a solid support.…”

“…30 Most recently, ruthenium nanoparticles incorporated into phosphine-modified nanoreactors catalyze the hydrogenation of benzoic acid whereas the corresponding unmodified nanoreactor was completely inactive; the efficacy of the phosphine-modified system was attributed to preferential absorption of the benzoic acid on the electron-rich RuNP surface. 31 However, ligand effects are not restricted to phosphine-based donors as amines have also been shown to modify the performance of Pt, Pd and Ru nanoparticles as catalysts for the hydrogenation of carbonyl compounds and nitroarenes by modifying surface electronic structure and/or steric properties. 32…”

“…While this is the first report of the use of a phosphine oxide modified polymer to stabilize RuNPs, there appear to be several recent examples of serendipitous oxidation of phosphine-decorated supports during the preparation of RuNPs, by impregnation with ruthenium trichloride, that were either not recognized as such or misinterpreted in the publication. 31,35 The most recent of these are microenvironment engineered RuNPs incorporated into phosphine-modified silica nanoreactors 31 and RuNPs stabilized by phosphorus-rich cross-linked network polymers. 35 Herein, we report detailed characterization of a range of phosphine oxide-decorated PIIL stabilized RuNPs together with comparative evaluation of their efficacy as catalysts for the hydrogenation of a range of carbonyl-based substrates.…”

Synthesis of Sulfonated Porous Organic Polymers with a Hydrophobic Core for Efficient Acidic Catalysis in Organic Transformations

“…However, in view of using alternative green, safe, cost‐effective, and environmentally benign synthetic strategies, a facile method based on free radical polymerization of vinyl‐functionalized monomers under solvothermal conditions has been developed [32] . Henceforth, a host of sulfonated porous organic polymers have been synthesized from self‐polymerization to copolymerization of various vinyl‐functionalized monomers such as p‐styrenesulfonate, triallylamine, triphenylphosphine, and 2,2′‐bipyridyl [33–38] . Nevertheless, it is still an ongoing research challenge to increase the concentration of acid sites without compromising the hydrophobicity of the parent organic polymers.…”