A zirconiumimidazolium metalorganic xerogel (Zr-bcmimCl) was synthesized via a simple gelation method. It showed high efficiency, selectivity, and reusability in esterification and transesterification, making it a promising catalyst for sustainable biodiesel production. Structural and electrochemical studies confirmed a robust, redox-active Zrligand network suitable for green energy applications.

Abstract

In this work, the synthesis and characterization of a novel zirconium-imidazolium-based metal–organic hydrogel and xerogel (Zr-bcmimCl) are described. The hydrogel was synthesized via a straightforward gelation process using zirconium oxychloride and 1,3-bis(carboxymethyl)-imidazolium chloride (bcmimCl) as precursors, followed by drying to obtain the corresponding xerogel (Zr-bcmimCl). The Zr-based hydrogel displayed moderate conductivity, and the interactions between zirconium species and the ligand may influence its redox properties, as observed by cyclic voltammetry measurements. In addition, the catalytic activity of metal–organic xerogel Zr-bcmimCl was successfully evaluated in the esterification of different carboxylic acids with various alcohols. The xerogel exhibited excellent conversion and selectivity while minimizing waste generation, as confirmed by green metrics. The catalyst also proved effective in transesterification reactions, achieving high yields in the conversion of triglycerides into fatty acid methyl esters, a key step in biodiesel production.