Facile synthesis of a covalently connected rGO-COF hybrid material by in situ reaction for enhanced visible-light induced photocatalytic H2 evolution

Covalent organic frameworks (COFs) have shown promising visible-light-driven hydrogen evolution activity, but improving the separation and migration of photogenerated electron-hole pairs is still the key point for further increasing their activity. In this work, for the first time, we designed and synthesized a new type of covalently connected rGO-COF photocatalyst for enhanced hydrogen evolution. A series of rGO-TpPa-1-COFs was obtained by a facile one-pot reaction through adding GO to the synthetic system of TpPa-1-COF with DMF as a solvent, which led to the reduction and functionalization of GO and further covalent connection with the COF as confirmed by various characterization techniques. The resulting rGO(5%)-TpPa-1-COF showed a H-2 evolution rate of 11.98 mmol g(-1) h(-1) under visible-light irradiation, which was 4.85 and 2.50 times higher than those of pure TpPa-1-COF and 5%rGO/TpPa-1-COF without any covalent connection between the two components, respectively. Further investigations confirmed that the covalent connection between the rGO and TpPa-1-COF components not only served as a band to tightly combine these two types of 2D material together, but also acted as a bridge to largely improve the separation of photogenerated charges of the COF as well as the migration of photogenerated electrons to rGO, thus leading to the resulting enhanced H-2 evolution activity.