Band Structure Engineering of Carbon Nitride: In Search of a Polymer Photocatalyst with High Photooxidation Property

The electronic band structure of a semiconductor photocatalyst intrinsically controls its level of conduction band (CB) and valence band (VB) and, thus, influences its activity for different photocatalytic reactions. Here, we report a simple bottom-up strategy to rationally tune the band structure of graphitic carbon nitride (g-C3N4). By incorporating electron-deficient pyromellitic dianhydride (PMDA) monomer into the network of g-C3N4, the VB position can be largely decreased and, thus, gives a strong photooxidation capability. Consequently, the modified photocatalyst shows preferential activity for water oxidation over water reduction in comparison with g-C3N4. More strikingly, the active species involved in the photodegradation of methyl orange switches from photogenerated electrons to holes after band structure engineering. This work may provide guidance on designing efficient polymer photocatalysts with the desirable electronic structure for specific photoreactions.