Ligand assisted hydrogenation of levulinic acid on Pt(111) from first principles calculations

Lars Gell,Karoliina Honkala

doi:10.1039/d1cy02048j

Abstract

In this study, we investigate the hydrogenation reaction of levulinic acid to 4-hydroxypentanoic acid on ligand-modified Pt(111) using DFT.

Highlights

Ligand design is crucial in creating self-assembled enzymelike reactant environments that control reaction mechanisms and achieve optimal enantioselectivity
We find that dissociated hydrogen from the Pt(111) surface can protonate the AQ ligand and discuss the role this plays on the mechanism of the hydrogenation reaction of levulinic acid (LA)
We investigated the adsorption of AQ ligands on Pt(111), the interaction between adsorbed AQ ligands, AQ protonation, and the hydrogenation of LA to 4-HPA on bare and AQ-modified Pt(111) surfaces using density functional theory (DFT)

Summary

Introduction

Ligand design is crucial in creating self-assembled enzymelike reactant environments that control reaction mechanisms and achieve optimal enantioselectivity. 19,28 Many ligandmodified late transition metal nanoparticles have shown catalytic activity 19 towards reactions such as the hydrogenation of organic acids, ketones and alcohols 29, the reduction of CO2 and the oxidation of C-C-double bonds. For hydrogenation reactions on Pt, cinchona alkaloid ligands have shown promising experimental results 9,11,32–34 such as high enantioselectivity in multiple ketone reduction reactions. Mation of biomass into value added products through hydrogenation reactions like the reduction of levulinic acid (LA) to γvalerolactone (GVL). 37,40,41 Several experimental and computational studies have shown the hydrogenation of LA can occur via homogeneous as well as heterogeneous catalysis. 42–47 The homogeneously catalyzed reduction of LA to GVL can be achieved using various transition metal complexes. 47 Lower reaction rates for the reduction of LA have been experimentally observed on Pt surfaces 45,50 compared to other transition metals (e.g. Ru, Pd) suggesting higher selectivity. Solvents with higher polarity than methanol, such as water, create a more favourable reaction environment thereby lowering the rate determining barrier by 0.1 eV. 47 Lower reaction rates for the reduction of LA have been experimentally observed on Pt surfaces 45,50 compared to other transition metals (e.g. Ru, Pd) suggesting higher selectivity. 51,52

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Results

Conclusion