C C formation mediated by photoinduced electrons from crystallized carbon nitride nanobelts under visible light irradiation

Abstract

Abstract Crystal structure and crystallinity of carbon nitride support, size and dispersity of active-metal nanoparticles (NPs), and surface engineering of composites have great roles in generation and separation of photogenerated charge carries and photocatalyzed organic reactions for the conversion of solar energy into chemical energy. Herein, we deposited well-dispersed Pd NPs with small size on crystallized carbon nitride (CN C) to construct a Schottky-type Pd/CN C hybrid for photocatalyzed Ullmann C C homo-coupling of aryl halides under visible light irradiation at room temperature. Compared to Pd NPs supported g-C3N4 (Pd/g-C3N4), Pd/CN C exhibits excellent visible light photocatalytic activity for Ullmann C–C coupling of aryl halides due to high crystallinity of CN C support, high dispersion and smaller size of Pd NPs, and the interfacial heterojunction of Pd/CN C. Upon visible light irradiation, more photogenerated electrons from CN C flow across the Schottky junction to metallic Pd and trigger the Ullmann C C coupling of aryl halides. The photogenerated holes on CN C surface are captured by a protic solvent (such as EtOH). In the presence of base K2CO3, the solvent undergoes dissociation, dehydrogenation, and finally can be oxidized by captured photogenerated holes. Moreover, Pd/CN C has general applicability for various substrates and shows excellent stability and reusability for more than nine cycles.