Synthesis and Structural Evaluation of Fe(III) Metal–Organic Frameworks formed from Terephthalic and Fumaric acids

Abstract

Iron-based metal–organic frameworks (Fe-MOFs) were synthesized at room temperature using Fe³⁺ ions with diprotic carboxylate linkers; terephthalic acid (H₂BDC) and fumaric acid (H₂FUM). The synthesized MOFs were characterized by Thermogravemetric (TGA), Brunauer-Emmett- Teller (BET), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX). Fe-BDC achieved the highest yield (68.97%) and Fe-FUM (48.14%). The solubility and TGA analysis revealed that Fe-BDC framework demonstrated superior hydrolytic and thermal stability at 500^oC compared to Fe-FUM MOF which showed partial hydrolysis and thermal stability at 450^oC. FTIR spectra confirmed coordination between Fe ions and carboxylate groups, with characteristic bands at 1596–1577 cm⁻¹ (νC=O), 1394–1396 cm⁻¹ (νC–O), and 504–557 cm⁻¹ (νFe–O). XRD patterns displayed broad, low-intensity peaks at 2θ = 12.17°, 26.64°, 30.64°, and 33.56°, indicative of amorphous structures typical of room-temperature syntheses. SEM images revealed irregular and aggregated particle morphologies, while EDX confirmed the presence of Fe, C, and O, validating successful framework formation, forming frameworks with distinct elemental ratios influenced by linker type. Fe-BDC exhibited metal-rich composition, while Fe-FUM was more organic-rich.