Magnetic iron/carbon nanorods derived from a metal organic framework as an efficient heterogeneous catalyst for the chemical oxidation process in water

Abstract

By one-step carbonization, metal organic frameworks (MOFs) can be conveniently turned into hierarchical hybrid materials which exhibit versatile functionalities. Even though theoretically all MOFs can be carbonized to yield carbon-based hybrids, iron-based MOFs seem to be suitable precursors owing to the abundance and low-toxicity of iron. While many iron-based MOFs have been developed, most of these MOFs are synthesized using DMF, a carcinogenic solvent. Thus, an iron-based MOF, MIL-88A, appears to be an ideal precursor because it can be prepared just in water. MIL-88A-derived carbonaceous material consists of iron oxide nanoparticles and porous carbon, making it a magnetic porous support/adsorbent. However, its iron content and porosity in fact can enable it to be a promising heterogeneous and magnetic catalyst for chemical oxidation, which, however, has not been investigated. Herein, MIL-88A was used to prepare a magnetic iron/carbon nanorod (MICN). The MICN was characterized and then evaluated as a heterogeneous catalyst to activate oxidants, including hydrogen peroxide and sodium persulfate to decolorize Rhodamine B (RB) dye in water. While RB could not be removed via the adsorption to MICN, and degradation by oxidants, the combination of MICN and oxidants successfully decolorized RB owing to the iron content of MICN which activated peroxide and persulfate through a Fenton-like reaction. In addition, MICN loading was found to be a more critical factor than the oxidant dosage for RB decolorization. Elevated temperature also improved the RB decolorization, whereas basic conditions were not favorable for MICN-activated oxidative processes. Ultrasonication represented a useful external facilitator to enhance the decolorization while the addition of ascorbic acid greatly inhibited the activation process. The recyclability of MICN was also demonstrated, showing that MICN could be reused for multiple cycles without regeneration treatment. These features enable MICN to be an effective and easy-to-recover chemical oxidative catalyst.