Synergistic engineering of intralayer conjugation and interlayer stacking within pyrene-based covalent organic...

Enhancing intralayer conjugation and interlayer π-π stacking within covalent organic frameworks (COFs) is an effective strategy to promote charge transport and separation. However, how conjugated substituents simultaneously regulate these structural features remains insufficiently understood. Herein, three pyrene-based COFs were comparatively investigated: Py-H COF (unmodified), Py-OMe COF (methoxy-functionalized, which enhances intralayer conjugation but weakens interlayer interactions due to steric effects), and Py-Vi COF (vinyl-functionalized, which simultaneously strengthens intralayer conjugation and interlayer stacking through an extended π-conjugated system formed between electron-rich vinyl groups and adjacent benzene rings). Theoretical analysis based on the Sr index reveals that Py-Vi COF exhibits the most pronounced intralayer charge separation (0.72) compared to Py-OMe COF (0.78) and Py-H COF (0.79). Consistently, calculated interlayer interaction energies indicate enhanced stacking stability in the order: Py-Vi COF (1.62 eV) > Py-H COF (1.35 eV) > Py-OMe COF (1.06 eV), in agreement with the interlayer distances derived from PXRD (3.73 Å for Py-Vi COF < 3.78 Å for Py-H COF < 3.84 Å for Py-OMe COF). Ultimately, the synergistic enhancement of intralayer conjugation and interlayer π-π stacking within Py-Vi COF promotes efficient charge transport and separation, resulting in a reduced exciton binding energy (38.08 meV) and prolonged carrier lifetimes (1083 ps). Consequently, Py-Vi COF exhibits superior photocatalytic performance, achieving a hydrogen peroxide production rate of 4262 μmol g^-1 h^-1 and high efficiency in amidation oxidation reactions. This work highlights a practical molecular design strategy for improving photocatalytic performance through the cooperative optimization of intralayer and interlayer charge transport within COF platform.