One-step, efficient and sustainable microwave-assisted biodiesel production using a sulfonated porous organic polymer catalyst

Abstract

The transition toward renewable fuels requires robust, recyclable, and eco-friendly catalysts for biodiesel synthesis. Here, we reported the synthesis process of a sulfonated covalent triazine framework-based porous organic polymer (CTF-POP-SO₃H) and the microwave-assisted esterification of oleic acid with methanol using a heterogeneous CTF-POP-SO₃H catalyst. The catalyst exhibited a high biodiesel conversion of 96.61% under optimized conditions (methanol-to-oil ratio, 20 : 1; catalyst loading, 8 wt%; reaction time, 50 min; temperature, 100 °C) with product formation confirmed by ¹H NMR, ¹³C NMR, and GC analyses. Comprehensive characterization of the catalyst was conducted using FTIR, BET, TGA, XRD, XPS, and SEM-EDX-MAPPING. The presence of acidic sites (–SO₃H) is confirmed by acid–base titration, which is well aligned with SEM-EDX-MAPPING. Kinetic evaluation revealed a low activation energy of 24.52 kJ mol⁻¹, while thermodynamic analysis indicated an endothermic process. Importantly, the catalyst retained over 80% of its activity after five successive cycles, confirming its durability and reusability. These results highlight that the sulfonated porous organic polymer is an efficient and sustainable catalyst for biodiesel production, providing an eco-friendly pathway aligned with global clean energy targets.