Synthesis, characterization and functionalization of MOFs and their use in Knoevenagel condensation reactions between ethyl cyanoacetate and 4-nitrobenzaldehyde

Abstract

Metal–organic frameworks (MOFs) are porous materials composed of metal ions, clusters and organic ligands. Due to their outstanding chemical, thermal, and solvent stability, as well as numerous unsaturated metal sites, they have proven to be useful catalysts. In this study, MOFs were synthesized using hydrothermal methods with terephthalic acid and Ca, Mg, Al, and Cr nitrates. Subsequently, they were functionalized with diethylamine. The formation of MOF-Al and MOF-Cr structures was confirmed through characterization via XRD, FT-IR, and CHN analyses. However, the synthesis did not yield MOF structures with Ca and Mg as metal ions; instead, phthalates of Ca and Mg were obtained. SEM images revealed the particle size and morphology of the particles, which ranged between 0.2 and 1 μm. TGA/DTA curves revealed that the functionalized MOFs were the most thermally stable. Textural analysis by N₂ adsorption/desorption showed that MOF-Cr and MOF-Cr-NH₂ had high BET area values of 1,769.67 and 998.22 m²g⁻¹, respectively. MOFs were employed as catalysts in Knoevenagel condensation reactions to synthesize (E)-ethyl 2-cyano-3-phenylacrylate and (E)-methyl 2-cyano-3-phenylacrylate, indicating their potential for reactions requiring acidic or basic sites.