Synergistic Catalysis of Ruthenium Nanoparticles and Polyoxometalate Integrated Within Single UiO−66 Microcrystals for Boosting the Efficiency of Methyl Levulinate to γ-Valerolactone

Abstract

The synthesis of heterogeneous cooperative catalysts in which two or more catalytically active components are spatially separated within a single material has generated considerable research efforts. The multiple functionalities of catalysts can significantly improve the efficiency of existing organic chemical transformations. Herein, we introduce ruthenium (Ru) nanoparticles (NPs) on the surfaces of a metal–organic framework pre-encapsulated with polyoxometalate silicotungstic acid (SiW) UiO−66 (University of Oslo [UiO]) and prepared a 2.0% Ru/11.7% SiW@UiO−66 porous hybrid using the impregnation method. The close synergistic effect of metal Ru NPs, SiW, and UiO-66 endow 2.0% Ru/11.7% SiW@UiO-66 with increased activity and stability for complete methyl levulinate (ML) conversion and exclusive γ-valerolactone (GVL) selectivity at mild conditions of 80°C and at a H2 pressure of 0.5 MPa. Effectively, this serves as a model reaction for the upgrading of biomass and outperforms the performances of the constituent parts and that of the physical mixture (SiW + Ru/UiO−66). The highly dispersed Ru NPs act as active centers for hydrogenation, while the SiW molecules possess Brønsted acidic sites that cooperatively promote the subsequent lactonization of MHV to generate GVL, and the UiO−66 crystal accelerates the mass transportation facilitated by its own porous structure with a large surface area.

POM@MOF Hybrids: Synthesis and Applications

“…More specifically, a one-pot synthesis was performed to include the [CoW12O40] 6− anion in the size matching cage of ZIF-8 (see Figure 13). During the Besides this increase in stability after the embedding of the POM in a MOF support, several groups have demonstrated the mutual activation of the POM guest and MOF support [32,119,127]. A very special and extreme example of such a synergism was demonstrated in the work of Kögerler et al [128].…”

Solidified and Immobilized Heteropolyacids for the Valorization of Lignocellulose

“…Additionally, Ru-H 4 SiW/MOF (M=Zr) catalysts were designed for the tandemhydrogenation/lactonization of ML to γ-valeroacetone . [122] The catalyst shows high activity and selectivity towards the desired product over five successive catalytic cycles.…”

“…The studies suggest that the balance of hydrogenation and hydrolysis, accordingly the acid/metal ratio, plays a crucial role in the optimization of the conversion and yield. Additionally, Ru‐H 4 SiW/MOF (M=Zr) catalysts were designed for the tandemhydrogenation/lactonization of ML to γ‐valeroacetone [122] . The catalyst shows high activity and selectivity towards the desired product over five successive catalytic cycles.…”

Water as Hydrogen Source for Highly Efficient Conversion of Biomass-Derived Levulinic Acid into γ-Valerolactone over Raney Ni Catalyst

“…Extensive studies on conversion of carbohydrate such as glucose and fructose to LA have been reported (Scheme 1). [17][18][19][20] The hydrogenation of LA into GVL with extra hydrogen source was performed in liquid-phase, gaseous-phase or supercritical CO2 systems by using different metal-based catalysts, such as Pd, Ru, Pt, Rh, Ni, Cu, Al. [5,10,14] Recently, formic acid, as a biomass derived, has been regarded as a material of hydrogen storage, which can be easily decomposed to molecule hydrogen at room temperature by catalytic conversion.…”