Construction and Activity of an All-Organic Heterojunction Photocatalyst Based on Melem and Pyromellitic Dianhydride

The separation efficiency of photogenerated carriers in the g-C3N4 system could be improved by the construction of all-organic heterojunctions. However, g-C3N4 has a large pi-pi conjugated plane that induces a low number of amino groups (-NH2), which are the sites of the heterojunction reaction with organic molecules. In this case, few heterojunction knots can be constructed, and the enhancement effect of the heterojunction cannot be fully displayed. In this study, an all-organic heterojunction with PMDA is constructed with melem instead of g-C3N4. Although the photocatalytic activity of melem is far below that of g-C3N4, the photocatalytic activity of PI (the all-organic heterojunction constructed with melem) is considerably higher than that of CP (the all-organic heterojunction constructed with g-C3N4). This result is attributed to melem that has more -NH2 groups to form more heterojunction knots, which can enable the effective transfer and separation of electron-hole pairs. These new findings may shed light on the design of all-organic heterojunction photocatalysts.