In-situ formatting benzisoxazole-linked covalent organic framework for enhanced photocatalytic hydrogen peroxide generation

Azole-linked covalent organic frameworks have drawn a lot of attention in photocatalytic synthesis of hydrogen peroxide, yet remain challenged by complex and costly synthetic routes. Here, we present a light-induced structural transformation strategy to facilely construct azole-linked covalent organic frameworks. We find that benzisoxazole linkages can be in-situ formed from imine linkages under light irradiation. As expected, the evolved partially benzisoxazole-linked covalent organic framework achieves a high hydrogen peroxide yield rate of 1986.9 μmol·g^-1·h^-1 in pure water. Theoretical calculations and spectral characterizations reveal significantly enhanced charge carrier separation and transfer efficiency, due to the formation of donor-acceptor structure. Furthermore, the in-situ formed benzisoxazole unit acts as both electron acceptor and catalytic center, promoting the reduction of dioxygen to superoxide radical, which is then converted into hydrogen peroxide, ultimately enhancing the yield. This work demonstrates a pioneering strategy for constructing benzisoxazole-linked covalent organic frameworks with high performance on hydrogen peroxide photo-synthesis.