Visible light-driven triazine-based S-scheme COF-TpTt@BiOBr heterojunction with oxygen vacancy for enhanced photocatalytic pollutants removal and hydrogen production.

S-scheme heterojunction is an effective tactic to improve photocatalytic property. But few studies on constructing heterojunction with BiOBr and covalent organic frameworks (COFs) are available. Herein, a novel series of COF-TpTt@BiOBr S-scheme heterojunctions with oxygen vacancies (OVs) were constructed via solvothermal method. COF-TpTt@BiOBr-10% showed enhanced photocatalytic performance under visible light. Pollutants (such as Methyl Orange (MO), methylene blue (MB), Rhodamine B (RhB), tetracycline (TC) and Levofloxacin hydrochloride (LEV)) can be efficiently degraded and the photocatalytic H generation rate reached 10828.075 μmol g h, which was 12.4 and 8.5 times of COF-TpTt and BiOBr. In addition, 3,3',5,5'-tetramethylbenzidine (TMB) oxidation experiment showed it has excellent molecular oxygen activation capacity. Furthermore, the S-scheme heterojunction charge transfer mechanism was proved by density functional theory (DFT) calculations. Under the influence of internal electric field, energy band bending and Coulomb force, e and h were efficiently separated and transferred. The formation of S-scheme heterojunction and generation of multiple free radicals assured the high redox activity of COF-TpTt@BiOBr-10% photocatalytic system. This study strengthened our deep understanding of S-scheme heterojunction charge transfer mechanism and offered a new way for high efficient hydrogen energy production.