Tuning CO₂ Capture and Conversion with Metal-Organic Frameworks Crystallized in Aqueous Graphene Oxide Suspensions

We present a green procedure for the synthesis of metal-organic frameworks (MOFs) (having Zn, Ni, or Co) in graphene oxide aqueous suspensions (obtained with graphitized or nongraphitized carbon nanofibers) avoiding organic solvents and high temperatures. The materials were thoroughly characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), N₂/CO₂-physisorption, Raman and X-ray photoelectron (XPS) spectroscopies. The results demonstrate that the nature of the metal (electronegativity) and graphene oxide (defects of oxygen-containing groups) are key in the size, porosity, and defectivity (free noncoordinated linkers and open metal sites) of the MOF and significantly affect their CO₂ adsorption energy (up to 6 kJ·mol^-1 increase), uptake (up to 5·mmol_CO2·g^-1 increase), and catalytic activity (up to 35% rate increase) with respect to bulk MOFs in the solvent-free, ambient pressure CO₂ cycloaddition to epoxides.