Synergistic promotion of ultra-small Pt nanoparticles and oxygen vacancy in MOF catalyst for ethyl levulinate to valerolactone at room temperature

Currently, designing highly efficient catalysts for biomass hydrogenation at low temperatures remains a significant challenge. This paper proposes a straightforward solvent-treatment strategy to create rich oxygen vacancies (OV), facilitating the loading of ultra-small (1.6 nm) Pt nanoparticles (NPs) onto a metal-organic framework (MOF) (LaQS) with rich O_V (LaO_V-r). Consequently, a bifunctional Pt₂/LaO_V-r catalyst, featuring Lewis acid and metal hydrogenation sites, was synthesized. Under mild conditions (80 °C), the Pt₂/LaO_V-r catalyst exhibited a catalytic yield of >99% in converting biobased ethyl acetylpropionate [ethyl levulinate (EL)] to valerolactone [γ-valerolactone (GVL)]. This yield was 3.2 and 13.3 times higher than those measured by Pt₂/LaQS and commercial Pt/C catalysts, respectively. Specifically, Pt₂/LaO_V-r catalyzed the full conversion of EL to GVL even at room temperature. The results revealed that the synergistic effect between ultra-small Pt NPs and O_V in the MOF catalyst is important for the efficient conversion of EL into GVL. Especially, the abundant O_V defects in LaO_V-r not only enhanced the electron cloud density of Pt NPs at active sites of hydrogenation, but also elevated the content of moderately-strong acidic sites. This enhances the ability to activate H₂ and EL, and promotes the intra-molecular dehydration of intermediates to GVL. The synergistic catalytic mechanism of O_V and ultra-small Pt NPs in MOFs is proposed. This study presents an effective strategy for defect engineering aimed at enhancing catalytic biomass conversion using MOFs-loaded metal NPs.