Hf-based metal organic frameworks as bifunctional catalysts for the one-pot conversion of furfural to γ-valerolactone

One-pot conversion of furfural to the target product γ-valerolactone (GVL) is a challenging and meaningful part of biomass exploitation. Development of heterogeneous catalysts with both Brønsted and Lewis acid properties has proved to be promising and useful because they offer an efficient way to tandem cascade reactions from furfural to GVL. Herein, we successfully synthesized sulfated DUT-67(Hf), a novel bifunctional catalyst, via a post-synthetic modification method. The prepared sulfated DUT-67(Hf) was characterized by XRD, SEM, TEM, N 2 adsorption-desorption, Elemental (N, C, H, S) analyses, situ infrared spectra of pyridine adsorptions, XPS, FT-IR, TG, and NH 3 -TPD. The acidity of the catalysts could be adjusted by submersion in different concentrations of aqueous sulfuric acid, giving 0.01 mol/L sulfuric acid for 0.42 mmol/g acidity to 0.1 mol/L sulfuric acid for 2.16 mmol/g acidity. Sulfated DUT-67(Hf) possessed by 0.06 mol/L aqueous sulfuric acid exhibited optimal catalytic activity and showed an 87.1% yield of GVL under the conditions of 180 °C after 24 h of reaction. Moreover, the mechanism of introducing Brønsted acid sites into DUT-67(Hf) and the better hydrogen donors was also investigated through contrasting experiments.