Fe-BTC Synthesis via Hydrothermal and Coprecipitation Routes: Towards Therapeutic Applications

Metal-organic frameworks (MOFs) are a class of materials with unique, tailorable properties[۱] that have garnered significant interest for biomedical uses, including bioimaging, biosensing, multimodal cancer treatments, and tissue engineering[۲-۷]. Due to their low toxicity, high drug-loading capacity, and versatile structures, iron-based metal-organic frameworks (Fe-MOFs) are among the most studied MOFS in the biomedical field[۸-۱۰]. Fe-BTC, commercially known as Basolite F۳۰۰, is a semi-crystalline MOF composed of Fe (II)/Fe (III) ions linked by ۱,۳,۵-benzenetricarboxylate acid (BTC) linkers[۱۱, ۱۲]. This composition can also form the crystalline MIL-۱۰۰(Fe), which exhibits distinct properties[۱۲, ۱۳]. Fig. ۱ shows the simulated XRD pattern of MIL-۱۰۰(Fe) and its structural units. As shown in this figure, MIL-۱۰۰(Fe) consists of tetrahedra formed by BTC-linked FeO۶ containing trimer units Fe-BTC shares this motif but lacks long-range order[۱۳]. Fe-BTC has been studied as a Magnetic resonance imaging (MRI) contrast agent and drug carrier[۳, ۱۴]. Additionally, it can catalyze the Fenton reaction, making it a potential agent for chemodynamic therapy [۱۵]. Therefore, Fe-BTC warrants further study in cancer treatment. In this study, hydrothermal and coprecipitation methods were utilized to synthesize Fe-BTC. In the hydrothermal method(H), appropriate amounts of Trimesic Acid and Ferric Chloride Hexahydrate were mixed in distilled water and heated at ۱۳۰°C for ۸ hours in a stainless-steel autoclave. Fe-BTC was also synthesized through coprecipitation using two different Iron sources, Ferric Nitrate Nonahydrate (C۱) and Ferric Chloride Hexahydrate (C۲). In this approach, appropriate amounts of Trimesic Acid and Ferric Nitrate Nonahydrate (Ferric Chloride Hexahydrate) were mixed in distilled water (sodium hydroxide solution) and stirred for two hours at room temperature. To investigate the crystal structure, morphology, and particle size, samples were characterized by X-ray diffraction and field-emission scanning electron microscopy (FE-SEM). The results were analyzed using OriginLab, ImageJ, and the PowerXRD Python package. The XRD patterns of all three samples showed the characteristic peaks of Fe-BTC, which were broader than those of MIL-۱۰۰(Fe), indicating the semicrystalline nature of the synthesized MOFs. Three peaks at ۱۲.۶°, ۱۴°, and ۳۷.۳° were also visible in the XRD pattern of sample H, but had lower intensity in the C۱ pattern and were absent in C۲'s. The observable increase in peak width (HC۱-C۲) and the absence of some peaks in C۲'s pattern suggested lower crystallinity in C۲ than in C۱, which in turn was lower than that of H. Assuming that the machine error and micro strain are negligible, the average crystallite sizes of H, C۱, and C۲ were calculated as ۸.۸۳ nm, ۴.۵۶ nm, and ۳.۴۶ nm, respectively, using Scherrer's equation. These results supported the overall conclusion that C۲ had the lowest crystallinity and that H had the highest. This also confirmed that the hydrothermal method provided high precursor solubility, enabling the formation of high-quality crystals. FE-SEM images of H showed aggregates of nanoparticles with well-defined polygonal surfaces and sharp edges. This morphology could also indicate higher crystallinity in the sample. The average nanoparticle size was about ۹۴ nm. Images of C۱ showed aggregated spherical nanoparticles with an average size of ۱۲۱ nm. In contrast, the images of C۲ showed micron-sized aggregates formed by layered Fe-BTC structures, with an average layer thickness of ۷۲۶ nm. Changes in crystallinity and morphology may have resulted from varying reaction rates between trimesic acid and iron sources in their reaction media, suggesting that crystallization was accelerated under hydrothermal conditions. At room pressure and temperature, the reaction occurred faster in the trimesic acid/ferric chloride hexahydrate/NaOH system. These findings confirmed that the Fe-BTC is highly tunable and can be synthesized with specific morphologies and sizes tailored for biomedical uses, such as cancer theranostics.

کلیدواژه ها:

Coprecipitation ، Fe-BTC ، Hydrothermal ، Metal-organic framework ، MIL-۱۰۰(Fe)