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

Abstract

The study of hydrogen peroxide production by O2 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 O2 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 O2 reduction sites, which realized the multi-site adsorption reduction of O2, and effectively enhanced the efficiency of photocatalytic O2 reduction to H2O2. The experimental results showed that the H2O2 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 O2 reduction to produce H2O2.