Green halogenation of aromatic compounds using environmentally friendly synthesized rod-like metal-organic framework (MIL-88A) catalyst

Abstract

Metal-organic frameworks (MOFs) have been extensively investigated as catalysts to synthesis of various chemical and eliminate toxic pollutants in water. Herein, MOF was used as an efficient catalyst for the halogenation of aromatic materials (aniline, b-naphthol, and naphthalene). The rod-like MIL-88A as an iron-based MOF was synthesized using Fe3+ with fumaric acid in water as a green solvent. The synthesized catalyst was characterized by FT-IR, XRD, SEM, and Raman. The rod-like MIL-88A is evaluated as the heterogeneous catalyst to activate KBr/I for the halogenation of aromatic compounds. 1HNMR and 13CNMR were used to characterize the halogenated aromatic materials. Halogenation of aromatic rings has been studied using potassium bromide (KBr) and potassium iodide (KI) as brominating and iodinating agents in the presence of rod-like MIL-88A as oxidant under solvent-free reaction (grinding) conditions. The halogenation yield of aromatics materials was 80–99%. The conversion yield of aniline to 4‑bromo aniline using 0, 10, 20, 30, 40, and 50 mg of rod-like MIL-88A at 25 min and room temperature (25 ºC) were 0%, 76%, 85%, 90%, 95%, and 88%, respectively. In addition, the conversion yield of B-naphthol to 1-Bromo-2-naphthol using a green catalyst was 97%. Also, the conversion yield of Naphthalene to 1-Bromonaphthalene using a rod-like catalyst. In most cases, mono-halogen derivatives were obtained in good yield without the aid of strong acids. In addition, the rod-like MIL-88A catalyst shows excellent stability and can be reused after proper washing treatments. It could be concluded that green synthesized rod-like MIL-88A could be used as an environmentally friendly catalyst for the halogenation of aromatics via grinding as a solvent-free reaction at room temperature.