Sustainable synthesis of iron-sludge derived MOFs : solvent-directed optimization for enhanced methylene blue degradation

Abstract The sustainable production of advanced materials from industrial waste becomes a cost-efficient and environmentally friendly strategy for functional catalysts. In this study, an Fe-rich industrial byproduct of iron metal sludge (IMS) was employed as a precursor in the development of conventional iron-based MOFs fixed with 1,3,5-benzenetricarboxylic acid (BTC) ligand but employing N, N-dimethylformamide (DMF) as solvent and modulator. The IMS-MOFs, prepared based on the different ratios of IMS: BTC: DMF, were systematically tested by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX), and cyclic voltammetry (CV) as well as electrochemical impedance spectroscopy (EIS) measurements coupled with Methylene Blue degradation tests. When the ratio of DMF was decreased, not much linker could coordinate and the crystallinity is weak; however, when larger amounts of DMF were added to the mixture, a more integral framework with better structural order and electrochemical activity could be obtained. With the optimal 1:2:400 ratio, the obtained IMS-MOFs owned more regular crystallinity and promoted charge transfer process, providing the maximum MB degradation efficiency. These results highlight the importance of DMF in controlling MOF growth and indicate that IMS can be a potential waste-derived precursor for green applications.