Utilizing ferrocene for doping iron into graphitic carbon nitride (Fe III /g-C 3 N 4 ): an internal dual photocatalyst for tandem oxidation/cyclization of toluene to benzimidazoles under visible light conditions.

Recently, doping metals into graphitic carbon nitride (g-C 3 N 4 ) is considered for environmental applications and organic reactions. In this study, we used ferrocene as a source of Fe 3+ to dope iron onto g-C 3 N 4 . The scaffold of the internal electric field is presented as an impressive strategy to increase photocatalytic activities. Fe 3+ was doped onto graphitic carbon nitride (Fe III /g-C 3 N 4 ) by the calcination method, which was well characterized by FT-IR, Raman, XRF, XRD, XPS, UV-visible DRS, photo-luminescence (PL), photocurrent, SEM, HR-TEM, EDX, BET, EIS, and cyclic voltammetry analyses. The synthesis of benzimidazole derivatives as pharmaceutically active compounds was introduced by using a suitable method under mild reaction conditions without using a base, oxidant, and other reagents or additives. The modification by using iron had a considerable effect on the optical and electronic characteristics in contrast to g-C 3 N 4 . The nanocomposite Fe III /g-C 3 N 4 could be employed as a multifunctional photocatalyst to perform the tandem process, oxidation of toluene, and then cyclization with o -phenylenediamines to prepare benzimidazoles under visible light conditions. The existence of the dynamic equilibrium of Fe 3+ /Fe 2+ helped in significantly improving the activity. By changing the reaction conditions and different control experiments as well as Mott-Schottky plot analysis, the superoxide ion (O 2 ˙ - ) can be obtained as the reactive species in this reaction. The photocatalytic activity of Fe III /g-C 3 N 4 for this one-pot reaction is also investigated in detail.