Fabricating MOF–GO Composites by Modulating Graphene Oxide Content to Achieve Superprotonic Conductivity

Metal-organic frameworks (MOFs) have emerged as crucial materials for proton conductivity, especially in the context of the growing need for alternative energy sources. Enhancing the proton conductivity of MOFs has been a major focus with one effective approach involving the integration of MOFs with graphene oxide (GO) to form composite materials. In this study, Cr-MIL-101 MOF is selected, and its growth on GO sheets has been achieved through in situ crystallization, leading to the formation of MOF-GO composites with varying GO content, MIL-101/GO(x%), (x = 1%, 2%, and 5%). The oxygen functional groups on the 2D-GO layer e.g., carboxyl, hydroxyl, and epoxy groups improve both the acidity and hydrophilicity of the composite, which directly contributes to improved proton conductivity. All the composites, fabricated in this work, exhibit higher conductivity than that of the parent MOF due to the additional acidic functional groups introduced by GO. Among the different composites, the MIL-101/GO(2%) composite exhibits the highest proton conductivity, achieving superprotonic conductivity value of 0.105 S cm^-1 at 80 °C and 98% relative humidity (RH). These results highlight the potential of MOF-GO composites for their application as nanofillers in proton exchange membranes for proton exchange membrane fuel cells (PEMFCs) and other energy-related technologies.