α-Fe@MIL-100(Fe) composites obtained by one-pot sonochemical synthesis

In this work, we present a one-pot synthesis route to prepare a new composite materials of iron (α-Fe) and a metal–organic framework (MOF) of iron, the MIL-100(Fe), using the sonochemical process. The experimental setup consists of applying high-power ultrasonic pulses to a water-dimethylformamide (H2O-DMF) (1:1) solution containing iron powder, 1,3,5-benzenetricarboxylic acid (H3BTC), and nitrate (NO3−). X-ray diffractions and the FT-IR measurements confirm that MIL-100(Fe) was obtained and the difference parameter Δ between the asymmetric and symmetric infrared mode of the order of 250 cm−1 is an indication that the carboxyl oxygen is coordinated through an unidentate interaction with iron Fe(III) in the MOF structure, also the presence of α-iron(Fe0) in the composite was confirmed by the appearance of the diffraction peak at 44.7°. Scanning electron microscopy showed a rod-like morphology for the MIL-100(Fe) and the magnetization measurements suggest a ferromagnetic behavior with maximum magnetization (MS) varying as a function of synthesis parameter Fe0, H3BTC, and nitrate ratio. Higher and lower MS, of 12.52 emu.g−1 and 0.34 emu.g−1, were obtained for Fe0:H3BTC:HNO3 ratio of 3:1:3.5 and 1:1:3.5, respectively. The largest and smallest Brunauer–Emmett–Teller surface areas of 1490.2 m2.g−1 and 666.4 m2.g−1 were obtained for the Fe0:H3BTC:HNO3 ratio of 1:1:3.5 and Fe0:H3BTC:NaNO3of 1:1:20, respectively. Decomposition of nitrate anion, NO_3^- and DMF, under ultrasound producing perhydroxyl radicals, HO2•, and hydrogen peroxide (H2O2) and hydrogen (H2) has been used to explain the mechanism for the α-Fe@MOF-100(Fe) magnetic composites preparation.