Density functional theory calculations on the solvatochromism of covalent organic framework Py-TT cluster compounds

Covalent organic frameworks (COFs) are stable porous materials linked by covalent bonds and have been the subject of considerable interest for a number of diverse applications, including catalysis, energy and optics. This study examined the solvent discoloration mechanism of the COF Py-TT cluster in a variety of solvent environments. Furthermore, density functional theory was employed to ascertain the spectral absorption characteristics and hole–electron attributes of clusters. These findings indicate that the solvent has a minimal effect on the pore area of Py-TT; however, the polarity of the solvent has a subtle influence on the diagonal of the pore structure. Additional calculations of the absorption spectrum indicated that the solvent induces a redshift in the absorption spectrum, with a greater redshift occurring in solvents of higher polarity, accompanied by an increase in the absorption intensity. Hole–electron distribution analysis indicated that the excited state of Py-TT was a comprehensive excitation of holes and electrons, with significant overlap. The increased polarity resulted in the centres of the holes and electrons moving away from each other, thereby reducing the overlap. However, this also resulted in a weakening of the Coulomb interaction, which facilitated electron transfer and caused the spectrum to shift towards the red end of the visible spectrum.