(513l) A DFT Study on the Catalytic Transfer Hydrogenation of Methyl Levulinate on a Defective Uio-66

γ-valerolactone (GVL) is an important building-block biomass compound, with applications as a solvent and in the synthesis of fine chemicals. GVL can be prepared by the catalytic hydrogenation of levulinic acids (LA) and levulinate esters (LEs) with H₂ gas or formic acid (HCOOH). This critical step is limited by high pressures required for H₂ or corrosivity of HCOOH. Recently, catalytic transfer hydrogenation (CTH) using secondary alcohols as hydrogen source has been found to be an effective method to selectively reduce LEs. Defect engineered metal-organic frameworks (MOFs) have also received much interest in heterogeneous catalysis due to the catalytic activity imparted by defects. Herein, we report a density functional theory (DFT) study on the CTH of methyl levulinate with 2-propanol as a hydrogen donor, on a defective UiO-66 created by removal of one linker. Three pathways are proposed and computed. In Pathway 1, the O-H bond of adsorbed 2-propanol is dissociated on the defective UiO-66, followed by concerted hydrogenation of methyl levulinate. Pathway 2 is a two-step process, initiated by the dissociation of C-H and O-H bonds of 2-propanol simultaneously, and followed by the concerted hydrogenation of methyl levulinate. Pathway 3 involves a Meerwein−Ponndorf−Verley (MPV) mechanism, initiated by the dissociation of O-H bond of 2-propanol on an open Zr site and the creation of another open Zr site by the removal of H₂O; this is followed by a step-wise hydrogenation of methyl levulinate involving a second 2-propanol. The calculated energy barriers show that Pathway 3 is the most favourable for the hydrogenation of methyl levulinate. The key rate-determining steps for the transfer hydrogenation process are also identified. Our results suggest that the defective UiO-66 may function as a potential catalyst for the CTH of LEs, which would assist in the future rational design of defect engineered MOFs for biomass upgrading.