Exploring the Brønsted acidity of UiO-66 (Zr, Ce, Hf) metal-organic frameworks for efficient solketal synthesis from glycerol acetalization.

Zr, Ce, Hf-based isostructural UIO-66 MOFs exhibited varying degree of Brønsted acidity (UiO-66(Hf) > UiO-66(Ce) > UiO-66(Zr)) on their secondary building units owing to the differences in their oxophilicities. UIO-66(Hf) showed remarkable catalytic activity for solketal synthesis with a turnover frequency as high as 13 886 h-1, which is 90 times higher than that of UiO-66(Zr) and several orders of magnitude higher than that of H2SO4 or Zeolites.