Halogenation of aromatic hydrocarbons by halide anion oxidation with poly(heptazine imide) photocatalyst

[Display omitted] •K-PHI photooxidizes halide anions (Cl―, Br―) in aqueous media with oxygen as an acceptor of electrons.•Chlorination as well as bromination of electron rich aromatic hydrocarbons is carried out by K-PHI photocatalyst.•Halogenation of aromatic hydrocarbons proceeds via in situ formation of “HOHal” species by two different pathways.•Solution of NaCl (seawater mimic) is a suitable reagent for photochlorination. Halocarbons have tremendous significance for the chemical industry. Arylchlorides and arylbromides are typically prepared via Friedel-Crafts reaction, using oxidative halogenation or employing halogen transfer agents, such as N-chloro- and N-bromosuccineimide. Herein, we show that K-PHI, a photocatalyst of the carbon nitride family, can easily photooxidize halide anions (Cl−, Br−) in aqueous media to promote oxidative halogenation of electron rich aromatic compounds. The technique is convenient, safe and gives the haloaromatic products with excellent yields from non-harmful starting reagents in the most sustainable fashion. We show that a solution of NaCl, mimicking seawater, can be used as a reagent for photochlorination.