2D-graphite carbon nitride/covalent organic framework heterostructure for enhanced photocatalytic H2 evolution

Heterojunctions composed of two-dimensional g-C₃N₄ (2D-CN) and covalent organic framework (TpPa-COF) were successfully prepared and named as 2D-CN/TpPa. TEM and XPS characterizations confirm that there is good contact between 2D-CN and TpPa-COF in the 2D-CN/TpPa. The fragmented 2D nanosheet structure of 2D-CN facilitates the formation of a more efficient heterojunction with TpPa-COF. 2D-CN/TpPa15 achieved the highest H₂ evolution rate of 19539 μmol g⁻¹ h⁻¹ under visible light irradiation, which is higher than that of BCN/TpPa15 (13,279 μmol g⁻¹ h⁻¹) and represented a 3.8-fold and 148-fold improvement over 2D-CN and TpPa-COF, respectively. DFT calculations indicate that 2D-CN possesses a higher W_f than TpPa-COF, thereby inducing the formation of a built-in electric field directed from TpPa-COF to 2D-CN in the 2D-CN/TpPa, which facilitates the migration of photogenerated electrons from the CB of 2D-CN to that of TpPa-COF under photoexcitation. Continuous experiments demonstrates that the photocatalytic activity of 2D-CN/TpPa15 remained stable following a 24 h photocatalytic reaction. This study proposes a promising strategy for developing g-C₃N₄-based composites with substantially enhanced photocatalytic performance.