Molecular engineering in thizolo[5,4-d]thiazole-based donor-acceptor covalent organic framework Induced high-efficient photosynthesis of H2O2

Covalent organic frameworks (COFs), as a newly emerging kind of porous and crystalline materials, serve as an ideal template for hydrogen peroxide (H 2 O 2 ) photosynthesis. However, the vision of achieving high efficiency and selectivity in H 2 O 2 photosynthesis is greatly hindered by the large exciton binding energy and limited charge separation efficiency influenced by the molecular structure of the building blocks. Herein, we developed three newly designed COFs with a donor–acceptor (D-A) structure and incorporated regulatory units (fluorine, F, and methoxyl, OCH 3 ) in the D-A pathway through molecular engineering to optimize electronic structure, the availability of activate sites, charge kinetics and O 2 activation capacity. Due to electron-donating effect, OCH 3 -functionalization (NIES-COF-3) can strengthen the intramolecular electron transfer and interaction with O 2 . This results in a reduction of the energy barrier of the rate-determining step (*O 2  → *OOH) and excellent O 2 -to-H 2 O 2 photocatalytic activity under visible light irradiation, delivering an H 2 O 2 production rate of 3238.4 μmol g −1 h −1 and a high apparent quantum yield of 3.17 %. In addition, F-functionalization (NIES-COF-2) primarily reduces the band-gap energy and improve the O 2 adsorption capacity compared to unfunctionalized NIES-COF-1. This work unveils insight into the catalytic activity-optimization mechanism of molecular engineering in the D-A structure and provides important references for photocatalysts.