Conversion of levulinic acid to γ-valerolactone over Zr-containing metal-organic frameworks: Evidencing the role of Lewis and Brønsted acid sites

Zr-containing UiO-66 and MOF-808 are evaluated for converting levulinic acid (LA) into γ-valerolactone (GVL) through various routes: (i) Step-wise esterification of LA to n-butyl levulinate (nBuL) Meerwein-Ponndorf-Verley (MPV) reduction GVL; (ii) One-pot two-steps with n-butanol followed by MPV sec-butanol; (iii) direct conversion GVL a tandem reaction. Selection this multistep complex reaction evidences the participation different sites (Lewis or Brønsted) material in each individual step: Brønsted-induced catalyze efficiently, while Lewis preferred step. Sulfation is used enhance Brønsted acidity MOF-808, which improves performance esterification. However, sulfate groups introduced detrimental step, since they reduce intra-pore space available form required bulky transition state. These results evidence need find best equilibrium between optimize outcome