Fabrication of pyridine incorporated and O-doped g-C3N4/COF: A type-II heterojunction for enhanced hydrogen production under visible light irradiation

The fabrication of heterojunction photocatalysts is important for achieving highly efficient electron transfer, charge separation, and catalytic activity. In this study, we report the successful creation of a type II heterojunction between pyridine incorporated and O-doped g-C 3 N 4 (POCN) and a covalent organic framework (COF). The heterojunction formation significantly reduced the fluorescence intensity of the POCN/COF, indicating effective separation of electron-hole pairs. Additionally, POCN/COF demonstrated excellent interface charge transfer resistance and photocurrent response. Its hydrogen production rate was remarkably high at 3500 μmol g⁻ 1 h⁻ 1 , about 1.6 times that of pure COF (2200 μmol g⁻ 1 h⁻ 1 ) and 3.5 times that of the physical mixture (1000 μmol g⁻ 1 h⁻ 1 ), and it also exhibited enhanced stability. This indicates that it can be effectively fabricated into a heterojunction of POCN and COF. The optimal value for adding POCN was approximately 5 wt% of COF. This demonstrates greater activity compared to other composite catalysts made from graphitic carbon nitride and COF. This study presents a valuable approach for fabricating reusable heterojunction photocatalytic systems and efficiently generating hydrogen from natural energy sources. A type II heterojunction photocatalyst called POCN/COF has been prepared by combining two materials: POCN and COF. This type II heterojunction helps separate electron-hole pairs effectively. • POCN and COF were synthesized into heterojunctions via a hydrothermal method. • The POCN/COF heterojunction produced hydrogen 1.6 times higher than POCN or pure COF. • Enhanced optical properties and hydrogen production resulted from the type II heterojunction.