We have prepared MIL-101/graphene oxide (GO) composites with various mixing molar ratio of Fe-containing metal– organic frameworks (MOFs) against GO. When synthesizing MOFs, it was possible to synthesize uniform crystal powders using hydrothermal method. MIL-101 consists of a terephthalic acid (TPA) ligand, with the central metal composed of Fe, which was the working electrode material for supercapacitors. Field emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analysis had been done to ascertain microstructures and morphologies of the composites. Cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge measurements were performed to analyze the electrochemical properties of the composite electrodes in 6 M KOH electrolyte. By controlling the metal ligand mole ratio against GO, we prepared a changed MOF structure and a different composite morphology, which could be studied as one of the promising optimized electrode materials for supercapacitors.

    Abstract 
    Graphical abstract
    1 Introduction
    2 Experimental section
        2.1 Materials
        2.2 Preparation of graphene oxide (GO)
        2.3 Preparation of MIL-101(Fe)
        2.4 Preparation of MIL-101GO composite
        2.5 Electrochemical characterization
        2.6 Structural characterization
    3 Results and discussion
    4 Conclusion
    Acknowledgements 
    References

• Hye Jin Oh(School of Chemical Engineering, Pusan National University)
• Seok Kim(School of Chemical Engineering, Pusan National University)