From metal–organic frameworks to magnetic nanostructured porous carbon composites: towards highly efficient dye removal and degradation

Abstract

A magnetic nanostructured porous carbon material (γ-Fe₂O₃/C) was easily synthesized using a microwave-enhanced high-temperature ionothermal method with an iron terephthalate metal–organic framework-MIL-53(Fe), as a template. The structure, morphology, magnetic properties, and porosity of γ-Fe₂O₃/C were characterized by powder X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, vibrating sample magnetometry, and Brunauer–Emmett–Teller surface area analysis. The obtained porous carbon materials (γ-Fe₂O₃/C), possessed a high specific surface area (397.2 m² g⁻¹) and pore volume (0.495 cm² g⁻¹). The adsorption properties were tested by removal of malachite green (MG) from an aqueous solution. After reaching adsorption equilibrium, the maximum adsorption capacity was 499 mg g⁻¹ at 30 °C, and reached 863 mg g⁻¹ at 60 °C. The excellent magnetism (20.10 emu g⁻¹) provided an ideal magnetic-separation performance. Analysis of the sorption kinetics and isotherms showed that these sorption processes were better fitted to the pseudo-second-order and Langmuir equations than pseudo-first-order and Freundlich equations. Various thermodynamic parameters, such as ΔG^θ, ΔS^θ, and ΔH^θ, were also calculated, and indicated that the present system was spontaneous and endothermic. It was further demonstrated that γ-Fe₂O₃ showed powerful photocatalytic activity for the degradation of MG under sunlight in the presence of H₂O₂.