12-Tungstophosphoric acid-encapsulated metal-organic framework UiO-66: A promising catalyst for the esterification of acetic acid with n-butanol

• HPW@UiO-66 was successfully synthesized by a one-pot hydrothermal method. • HPW was incorporated into the UiO-66 structure with a uniform distribution. • The highest conversion of acetic acid (80.2%) was achieved over 30HPW@UiO-66. • HPW@UiO-66 showed high structure stability and reusability. • An Eley-Rideal model mechanism for the esterification reaction was proposed. The synthesis of highly efficient and stable heteropolyacids catalysts for the esterification of acetic acid with n -butanol is an urgent task. In this work, a novel series of 12-tungstophosphoric acid-encapsulated metal-organic framework UiO-66 materials (HPW@UiO-66) with different HPW loadings were successfully prepared via a one-pot hydrothermal method. The synthesized materials were systematically studied by FT-IR, PXRD, N 2 adsorption, ICP-OES, SEM, TEM, TGA-DTG, NH 3 -TPD and XPS. Under the optimum reaction conditions of 120°C temperature, 2:1 n -butanol/acetic acid molar ratio, 3.0 wt% catalyst amount, and 3 h reaction time, the highest conversion of acetic acid (80.2%) was achieved over 30HPW@UiO-66. The highest activity of 30HPW@UiO-66 could be attributed to its high dispersion of HPW, suitable specific surface area, total volume and total acidity. Meanwhile, the 30HPW@UiO-66 cycled to the fourth time still exhibited good catalytic activity. Moreover, an Eley-Rideal mechanism for the esterification reaction over the HPW@UiO-66 was proposed. Overall, the results demonstrated the potential of HPW@UiO-66 for the esterification process.