Spatiotemporal Spectroscopy of Fast Excited-State Diffusion in 2D Covalent Organic Framework Thin Films.

Covalent organic frameworks (COFs), crystalline and porous conjugated structures, are of great interest for sustainable energy applications. Organic building blocks in COFs with suitable electronic properties can feature strong optical absorption, whereas the extended crystalline network can establish a band structure enabling long-range coherent transport. This peculiar combination of both molecular and solid-state materials properties makes COFs an interesting platform to study and ultimately utilize photoexcited charge carrier diffusion.

Understanding the electronic pi-system of 2D covalent organic frameworks with Wannier functions.

We investigate a family of hexagonal 2D covalent organic frameworks (COFs) with phenyl and biphenyl spacer units and different chemical linker species. Chemical trends are elucidated and attributed to microscopic properties of the [Formula: see text]-electron-system spanned by atomic [Formula: see text]-orbitals. We systematically investigate the electronic structure, delocalization of electronic states, effects of disorder, bond torsion, and doping, and correlate these with variable [Formula: see text]-conjugation and nucleus-independent chemical shift (NICS) aromaticity.