Boosting catalytic transfer hydrogenation of alkyl levulinate to γ-valerolactone using ionic liquid modified UiO-66

An effective strategy is proposed here for transfer hydrogenation of alkyl levulinate to γ-valerolactone (GVL) using a UiO-66 framework modified with phosphotungstate ionic liquid (UiO-66@IL(HPW)). Due to the intensive influence of ionic liquid fragment, the modification significantly enhances the catalytic activity of UiO-66@IL(HPW), leading to a complete conversion of ethyl levulinate with over 93.1% selectivity for GVL. Characterizations techniques, including XRD, N 2 absorption/desorption, SEM, FT-IR, pyridine FT-IR, NH 3 -TPD and CO 2 -TPD, confirm that while the basic structure of UiO-66-NH 2 is insignificantly changed, the introduction of the ionic liquid greatly improves the acidic/base properties of the catalyst. XAFS and XPS results reveal an intensive interaction between the N and W species in UiO-66@IL(HPW), and the formed W-N/O moiety is responsible for the enhanced catalytic activity. In addition, a plausible catalytic mechanism is proposed based upon in situ DRIFTS and density functional theory (DFT) calculations, highlighting the crucial role of ionic liquid fraction within the UiO-66 ligand. Therefore, this work would contribute to the valorization of biochemicals.