Fluorination of the tertiary carbon at the edge of graphene oxide

A well-defined controlled selective edge functionalization of graphene oxide (GO) is of high interest because it allows tuning the chemical and physical properties of graphene oxide with minimal damage to the carbon at the basal plane. The present work reports a rapid one-step synthesis of edge fluorinated graphene oxide (FGO) from GO in an aqueous medium. A selective fluorination of the tertiary carbon at the edge of GO was achieved by chemoselective substitution of the carboxylic acid with fluorine in one hour following a decarboxylative fluorination technique using 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (SELECTFLUOR) and silver ion catalyst. The structure and composition of FGO were characterized by multiple analytical techniques, such as TEM, SEM, XRD, EDS, FTIR, XPS, Raman spectroscopy, etc. As observed in XPS and NMR analysis, the decarboxylative fluorination of GO resulted in the formation of covalent C–F bonds at the edge. The absence of the peak associated with the C–F group on the basal plane in 19 F NMR clearly indicates the fluorination at the edge of GO. Most importantly, similar linewidth and spectral patterns in proton-decoupled 19 F{ 1 H} and proton-coupled 19 F NMR spectra of FGO suggest that the fluorine atoms are bonded to the tertiary carbon atom. The selective functionalization of the tertiary carbon at the edges of GO achieved here, is unprecedented. The fluorine group at the edge of GO can act as a new reaction center for subsequent chemical modification. This simple edge-controlled fabrication method described here provides a facile pathway to fabricate multifunctional GO and expand their potential applications. Graphical abstract