Publication date: 11th July 2022
Two-dimensional covalent organic frameworks (2D COFs) are crystalline porous polymers characterized by long-range order and well-defined open nanochannels. 2D COFs are promising for applications in electronics, catalysis, sensing, and energy storage. The development of highly conductive 2D COFs has remained challenging due to the finite π-conjugation along the 2D lattice and defects introduced by grain boundaries. Furthermore, the charge transport mechanism within the crystalline framework has remained elusive. We use time- and frequency-resolved terahertz spectroscopy to reveal intrinsically Drude-type band transport of charge carriers in semiconducting 2D COF thin films condensed by 1,3,5-tris(4-aminophenyl)benzene (TPB) and 1,3,5-triformylbenzene (TFB). The TPB–TFB COF thin films demonstrate high photoconductivity with an exceptionally long charge scattering time exceeding 70 fs at room temperature which resembles crystalline inorganic materials. This corresponds to a record charge carrier mobility of 165 ± 10 cm2 V–1 s–1, vastly outperforming that of the state-of-the-art conductive COFs. These results reveal TPB–TFB COF thin films as promising candidates for organic electronics and catalysis and provide insights into the rational design of highly crystalline porous materials for efficient and long-range charge transport.