Unveiling catalytic mechanism for highly selective production of hydrogen peroxide on nitrogen-rich conjugated covalent organic frameworks

Covalent organic frameworks (COFs) belong to porous materials with tunable skeletons and porosities. Oxygen reduction reaction (ORR) on COF can generate H₂O₂. However, experimental evidences for the catalytic mechanism are currently needed. In this work, a structure model of pyrazine nitrogen-containing COF (PN-COF) prepared by hydrothermal reaction is applied to study the H₂O₂ generation. Because hydrothermal environment significantly drives the polycondensation of precursors to form large building units, the obtained PN-COF shows high conductivity (2.47 × 10⁻³ S m⁻¹). Thus, extremely high selective conversion of H₂O₂ production up to 99 % is achieved catalysed by PN-COF. Theoretical DFT calculations, and in situ Fourier-transform infrared spectra, in situ Raman and in situ electron paramagnetic resonance measurements confirm that the pyrazine molecule in PN-COF undergoes a structural evolution resulting in an active site and the generation of 1,4-endoperoxide species (*OO*) on PN-COF. The catalytic mechanism of one-step two-electron pathway is unveiled. These results provide theoretical guidance for design of highly selective and efficient non-metal electro catalysts.