A Series of UiO-66(Zr)-Structured Materials with Defects as Heterogeneous Catalysts for Biodiesel Production

As a result of the demand overload for energy and elevating the prices of crude oil, countries are seeking for finding alternative energy sources. Biodiesel (mono alkyl ester) is an ideal candidate due to several merits, such as environmental friendliness, higher combustion efficiency, carbon neutrality, and low sulfur content. Herein, a series of UiO-66­(Zr)-structured materials with defects were utilized as solid catalysts for the esterification reaction of oleic acid to generate biodiesel based on our earlier work about the preparation of defective-type UiO-66­(Zr) materials by a green approach. The catalytic results indicated that the order of catalytic activity was UiO-66­(Zr)-NH₂ > UiO-66­(Zr)-NO₂ > UiO-66­(Zr). The yield (97%) and selectivity (100%) of biodiesel could be achieved at 60 °C for 4 h, which was better than UiO-66­(Zr) prepared by a conventional method (40%). Additionally, these catalysts had the capacity to be proficiently recyclable and utilized again. The kinetic study indicate that a low activation energy (E_a = 15.13 kJ mol^–1) over UiO-66­(Zr)-NH₂ was desired for the reaction.