Enhancement of the visible-light absorption and charge mobility in a zinc porphyrin polymer/g-C3N4 heterojunction for promoting the oxidative coupling of amines

Graphitic carbon nitride (g ­ C3N4, CN) has been widely used as a photocatalyst due to its high stability and suitable band gap. However, its further development is limited due to inefficient light harvesting and rapid recombination of photogenerated carriers. In this study, a visible-light-responsive zinc porphyrin (ZnP)/CN heterojunction photocatalyst was synthesized by the combination of CN and a zinc-porphyrin-conjugated microporous polymer (ZnP-CMP). ZnP/CN exhibited excellent photocatalytic activity for the oxidative coupling of amines to imines under visible-light irradiation. The efficiency of the as-developed photocatalyst was 25 times greater than that of CN and about 2 times greater than that of ZnP-CMP. The significantly enhanced catalytic efficiency was attributed to the promotion of visible-light harvesting and photogenerated charge mobility via the introduction of ZnP-CMP. The ZnP/CN heterojunction photocatalyst also exhibited excellent broad substrate scope, stability, and reusability.