Hyper-Cross-Linked Microporous Polymers as Cheap and Efficient Catalysts for the Synthesis of Biodiesel

In this work, we report a series of hyper-cross-linked sulfonated polymers, structurally related to PIMs, as highly efficient and versatile catalysts for biodiesel production. By tuning monomer composition to increase aromatic content, we generate porous polymers with tailored surface areas and porosity, which are thoroughly characterized and assessed for CO2/N2 separation. These catalysts promote both Fischer esterification of free fatty acids and transesterification of triglyceride oils derived from the same fatty acids, achieving over 95% conversion to fatty acid methyl esters (FAME) in 24 h or less under diverse conditions. Remarkably, by using a variety of oils, high activity is maintained even with reduced catalyst and methanol loadings, demonstrating intrinsic efficiency and robustness. The polymers prove to be fully scalable and recyclable, retaining performance over multiple cycles and efficiently converting waste cooking sunflower oil with comparable yields to pure edible oils. This work establishes a direct structure–property–performance relationship, linking polymer architecture and porosity to catalytic activity, and provides a versatile, sustainable platform for next-generation porous catalysts in biodiesel production and broader chemical transformations.