Linker length-dependent hydrogen peroxide photosynthesis performance over crystalline covalent organic frameworks

Molecular engineering-tuned covalent organic frameworks (COFs) have been demonstrated as promising photocatalysts for photocatalytic hydrogen peroxide (H2O2) production by a two-electron oxygen reduction in water. Herein, a simple strategy by altering the linker length of the building units is developed to harvest efficient COF catalysts for H2O2 photosynthesis. Three imine-linked COFs with similar structures but varied amine linker lengths were prepared by the amine aldehyde condensation reactions. It was found that the resultant COF with a longer linker exhibited a higher H2O2 generation rate. The highest H2O2 production rate of the prepared COFs with the longest amine linker reached 1164 & mu;mol h(-1) g(cat)(-1) in O-2-presaturated pure water, together with better stability. The rising photocatalytic performance of COFs with longer linkers could be attributed to the tuning of their molecular structures and morphologies, including a more negative conductor band, higher specific surface area, and separation efficiency of photogenerated carriers. This study provides a simple strategy by facially varying linker lengths for gaining COF-based photocatalysts.

Automated summary

A simple strategy of altering linker length in covalent organic frameworks (COFs) has been developed to fabricate efficient photocatalysts for hydrogen peroxide (H2O2) synthesis. By varying the linker length, three imine-linked COFs with similar structures but different amine linker lengths were successfully prepared. It was found that COFs with longer linkers exhibited higher H2O2 generation rates. This study provides a simple strategy for obtaining COF-based photocatalysts by facially varying linker lengths.