Monday, 24 February, 2014
Oriented Thin Films of a Benzodithiophene Covalent Organic Framework
D. Medina, V. Werner, F. Auras, R. Tautz, M. Dogru, J. Schuster, S. Linke, M. Döblinger, J. Feldmann, P. Knochel, and T. Bein -
ACS Nano, Vol. 8 (4), pp 4042-4052 (2014)
A mesoporous electron-donor covalent organic framework based on a benzodithiophene core, BDT-COF, was obtained through condensation of a benzodithiophene-containing diboronic acid and hexahydroxytriphenylene (HHTP). BDT-COF is a highly porous, crystalline and thermally stable material, which can be handled in air. Highly porous, crystalline oriented thin BDT-COF films were synthesized from solution on different polycrystalline surfaces, indicating the generality of the synthetic strategy. The favorable orientation, crystallinity, porosity and the growth mode of the thin BDT-COF films were studied by means of X-ray diffraction (XRD), 2D grazing incidence diffraction (GID), transmission and scanning electron microscopy (TEM, SEM) and krypton sorption. The highly porous thin BDT-COF films were infiltrated with soluble fullerene derivatives, such as [6,6]-phenyl C61 butyric acid methyl ester (PCBM), to obtain an interpenetrated electron-donor/acceptor host-guest system. Light-induced charge transfer from the BDT-framework to PCBM acceptor molecules was indicated by efficient photoluminescence quenching. Moreover, we monitored the dynamics of photo-generated hole-polarons via transient absorption spectroscopy. This work represents a combined study of the structural and optical properties of highly oriented mesoporous thin COF films serving as host for the generation of periodic interpenetrated electron-donor and electron-acceptor systems.