Robust Nanowrapping of Reduced Graphene Oxide by Metal-Organic Network Films between Fe Ions and Tetra(Catechol-Substituted) Porphyrin.

We found the utilization of porphyrin-based metal-organic network films composed of tetra(catechol-substituted)porphyrin (cPor) and Fe ions for robust wrapping materials of graphene oxide (GO), which can keep the dispersion state under the chemical reduction of GO to reduced graphene oxide (rGO) in water. The tetra(catechol-substituted)porphyrin (cPor) was designed for soft-wrapping methods because the aromatic porphyrin moieties can be strongly adsorbed onto the surface of GO or rGO via both π-π interactions and the catechol-Fe coordination network formation. The GO sheets covered with the cPor-Fe films were reduced chemically in water under retention of the wrapped nanostructure of the cPor-Fe/GO sheets. The obtained rGO composites after chemical reduction are characterized by using UV-vis absorption, Raman, and X-ray photoelectron spectroscopy (XPS) spectra, as well as thermogravimetric analysis and energy-dispersive X-ray spectroscopy (EDX). XPS and EDX spectra showed the presence of Fe species, which originates from the coordinated Fe-catechol nodes in the wrapped cPor-Fe films. The wrapped rGO sheets could be easily handled in water because of their high solubility therein and exhibits electric conductivity. In dynamic light scattering analysis, the average diameter of rGO composites before and after reduction changed slightly from 419 ± 309 to 663 ± 697 nm, indicating that the chemical reduction is not significantly influenced by the size of the rGO composite or the solubility. It is expected that the soft wrapping cPor-Fe/rGO should employ the applications to prepare functional materials such as modified electrodes, catalysts, energy-storage materials, and electronic devices.