Photocatalytic ipso-nitration of bromophenol intermediates on Ag/g-C3N4

An energy-saving and friendly process was performed on the Ag/g-C3N4 photocatalyst to achieve the halo-nitro-phenol intermediates with the ipso-nitration of bromophenols and nitrite. As detected by SEM, TEM and XRD, Ag nanoparticles are proved to be located on the surface of g-C3N4 and lead to the improvement of photocatalytic ability by UV–vis, PL spectra and photoelectronic analysis. The substituents of bromophenols could be immediately related to their regioselective conversion. The fluoro-, chloro-, and bromo-substituted bromophenols revealed the higher nucleophilic potential than the alkyl- and alkoxyl-substituted ones. From the inhibition experiment and EPR analysis, the photo-generated superoxide and active holes played crucial roles in photocatalytic nitration through the peroxynitrite way into ·NO2 radicals. Finally, the electrostatic potentials of all bromophenols were calculated on Gaussian09 W software to explain the distribution of photo-driven nitration products.