Asymmetric acceptor-donor-acceptor type covalent organic frameworks with dual O2 reduction moieties for boosting H2O2 photosynthesis.

• A novel A1-D-A2 type photocatalyst is designed for H 2 O 2 evolution. • The photocatalytic H 2 O 2 evolution activity is obviously enhanced. • Asymmetric receptor units induced efficient charge separation. • Dual reduction sites are confirmed to promote O 2 reduction to H 2 O 2. The study of hydrogen peroxide production by O 2 reduction reaction using covalent organic framework (COF) photocatalysts has attracted extensive attention in recent years. However, there are still great challenges in accurately controlling their structures to achieve rapid carrier separation and efficient O 2 reduction. Based on this, we constructed the A1-D-A2 COF photocatalytic material (TT-DTDA-COF) with asymmetric dual acceptor sites by connecting thieno [3,2-b] thiophene, benzene, and triazine as the basic units through imine bonds. Under the synergistic effect of thieno [3,2-b] thiophene and triazine electron acceptors, the separation and transfer efficiency of TT-DTDA-COF photogenerated carriers was significantly enhanced. At the same time, according to the in-situ infrared and DFT calculation results, it was found that these two acceptor units served as O 2 reduction sites, which realized the multi-site adsorption reduction of O 2 , and effectively enhanced the efficiency of photocatalytic O 2 reduction to H 2 O 2. The experimental results showed that the H 2 O 2 generation rate of TT-DTDA-COF with A1-D-A2 dual receptor structure was 1302 μmol·g−1·h−1 under visible light irradiation, which was 3.4 times higher than that of TB-DTDA-COF with single receptor D-A structure and higher than that of most of the materials reported so far. This study provides a new idea for accurately designing COF-based photocatalysts to achieve efficient O 2 reduction to produce H 2 O 2. [ABSTRACT FROM AUTHOR]