Harnessing the Catalytic Potential of Copper Oxide Nanoparticle-Confined Amine-Functionalized Pore-Engineered COFs for High-Efficiency Transesterification

The growing global concern over rising carbon emissions necessitates the development of sustainable alternatives to conventional nonrenewable fuels such as oil and diesel. Current catalysts for biodiesel production via transesterification face drawbacks such as soap formation, leaching, poor reusability, and sensitivity to feedstock impurities. Considering the limitations of current catalytic systems, a pore-engineered covalent organic framework was synthesized. In the present work, a urethane-linked covalent organic framework was functionalized with ethylene diamine to obtain free amine groups in the cavity to obtain a solid base catalyst for transesterification. This pore-engineered UCOF was confined with CuO NPs to enhance its catalytic efficiency. The catalyst was well characterized using various sophisticated techniques like Fourier transform infrared, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Brunauer–Emmett–Teller, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The BET surface area and pore diameter analysis also supported the pore engineering and confinement of the CuO NPs. Transesterification of triacetin with methanol as a model reaction for biofuel production was carried out in a one-step process to produce methyl acetate. All the process parameters such as the triacetin/methanol ratio, catalyst amount, temperature, and time were optimized to obtain >99% conversion of triacetin. The reaction follows pseudo-first-order kinetics, and the rate constant was determined to be 1.31 h–1, and the Arrhenius activation energy was calculated as 76.72 kJ mol–1. The scope of this catalyst was extended for complete transformation of castor oil to its respective fatty acid methyl ester, i.e., biodiesel. The catalyst opens up horizons for the transformation of nonedible and waste cooking oil to useful biodiesel to solve the global issue of depleting fuels.