Polythiophene Doping of Metal-Organic Frameworks Using Innate MOF-Catalyzed Oxidative Polymerization

The copper- and iron-containing metal-organic frameworks
(MOFs) HKUST-1 and MIL-100(Fe) absorb organic molecules into their pores. When loaded with electron-rich oligothiophenes, these MOFs react under heat to initiate oxidative polymerization of entrapped monomers. This reaction is not observed in the non-redox-active MOF MIL-100(Al). The resulting MOF composites contain conjugated polymer dopants trapped inside their pores, causing profound shifts in the composite electronic structure. We have characterized the composites by infrared, Raman, and UV-visible spectroscopy and examined their structure using confocal microscopy, scanning electron microscopy, and atomic force microscopy. Reasoning from TD-DFT calculations of an HKUST-1 model system bound to monomers, we rationalize the observed reactivity and propose an initiation mechanism based on a ligand-to-metal charge transfer state.