Metal-Free Covalent Organic Frameworks Containing Precise Heteroatoms for Efficient Oxygen Reduction Reaction

Heteroatom-doped carbon-based nanomaterials are one of the most promising metal-free electrocatalysts due to their high activity, low cost, long lifetime, and environmental friendliness. However, the precise atomic position is hard to tune; moreover, the specific role of those heteroatom species is still unclear. Herein, we report a series of metal-free benzotrithiophene-based covalent organic frameworks containing various heteroatoms (Se, S or O), BTT-COFs (named JUC-616, JUC-617, and JUC-618, respectively), and explore their oxygen reduction reaction (ORR) catalytic activity. Remarkably, JUC-616 involving precise Se atoms exhibits an onset potential of 1.02 V and half-wave potential of 0.78 V, which is the best among metal- and pyrolysis-free COF-based electrocatalysts reported so far. Furthermore, we demonstrate that the high ORR catalytic performance of JUC-616 can be attributed to the small free energy and overpotential by DFT calculations. This work thus promotes the promising potential of functionalized COFs with precise heteroatoms for electrocatalysts.