ZnO/Cu-BTC metal-organic frameworks as a heterogeneous catalyst for efficient transformation of waste cooking oil into biodiesel

Metal-organic frameworks (MOFs) are widely regarded as promising materials in the field of catalysis due to their unique properties, including large porosity, high surface area, and adjustable properties. In this study, facile and efficient heterogeneous catalysts were prepared by modification of a copper-based MOFs constructed from 1,3,5-benzenetricarboxylate (BTC) with zinc oxide (ZnO/Cu-BTC), and the composite was applied as a catalytic agent for biodiesel production using waste cooking oil (WCO) as the feedstock. Characterization techniques, such as XRD, SEM, TEM, FTIR, TGA and N₂ adsorption-desorption, were employed to analyze the catalyst, which was then used for the conversion of WCO into biodiesel. We characterized the resulting biodiesel using GC-MS and NMR. The ZnO/Cu-BTC catalyst exhibits an impressive biodiesel conversion of 92.4 % under optimum conditions of 4 wt% catalyst loading, 20:1 methanol/WCO molar ratio at 160 °C for 4 h. This efficiency is ascribed to the synergistic action of the bimetallic components, coupled with enhanced surface properties. Additionally, ZnO/Cu-BTC catalyst showed excellent durability, maintaining 84.1 % conversion even after three reaction cycles. Kinetics investigation showed that the transformation to biodiesel proceeds via pseudo-first order kinetics. In comparison with other solid catalysts reported in previous studies, ZnO/Cu–BTC catalyst showed good WCO biodiesel conversion. The biodiesel conformed to ASTM6751 fuel standards, indicating successful performance. Finally, the results presented in this study show that ZnO/Cu–BTC catalyst is an effective solid catalyst for the conversion of WCO to biodiesel.