Ultrathin Crystalline Covalent‐Triazine‐Framework Nanosheets with Electron Donor Groups for Synergistically Enhanced Photocatalytic Water Splitting

Abstract

Ultrathin nanosheets demonstrate great potential for photocatalytic applications, however, suffer from enlarged bandgap and narrowed visible-light-responsive range due to the quantum confinement effect. Herein, we report a novel redox strategy for efficient preparation of ultrathin crystalline amide-functionalized covalent-triazine-framework nanosheets (CTF NSs) with enhanced visible light absorption for the first time. The obtained CTF NSs exhibited remarkable photocatalytic hydrogen (512.3 μmol h -1 ) and oxygen (12.37 μmol h -1 ) evolution rates, 17 and 23 times higher than that of pristine bulk CTF, respectively. Moreover, the photocatalytic overall water splitting could also be achieved by the CTF NSs with efficient stoichiometric H 2 (5.13 μmol h -1 ) and O 2 (2.53 μmol h -1 ) evolution rates under visible light irradiation, which is superior to previous CTFs/covalent-organic frameworks-based photocatalytic materials. Experimental and theoretical analysis revealed that introduction of a small amount of amide groups as electron donor in the CTF NSs could optimize its band structure and improve its visible-light absorption, hydrophilicity and carrier separation efficiency, thus resulting in significantly enhanced photocatalytic performance. Additionally, the well-dispersed CTF NSs could be easily casted onto a support as a thin film device and demonstrate excellent photocatalytic activity (25.7 mmol h -1 m -2 for hydrogen evolution), which has rarely been achieved before.