In an earlier report, we found that neat 3,4-ethylenedioxythiophene (EDOT) directly reacts with HKUST-1 to form a core-shell composite in which the HKUST-1 surface is coated with conjugated polymer, while unsubstituted thiophenes formed a filled composite where polythiophene is contained in the MOF's pores. In this work, we found that EDOT and 3-methoxythiophene (3MOT), which react in the neat form to form core-shell composites, can be loaded into HKUST-1 pores without reaction when dissolved in hexanes. To a lesser extent, 3-hexyloxythiophene (3HOT) can be loaded in the same way. These hexane-loaded composites can then be heated, resulting in the formation of a 'filled' composite. This finding allows us to choose to prepare either a core-shell or a filled composite by selecting reaction conditions. The process of heating with alkoxythiophenes results in a morphology change in the HKUST-1 material. Composites were characterized by nitrogen sorption measurements, powder X-ray diffraction, and vibrational spectroscopy.

The copper-based metal-organic framework (MOF) HKUST-1 adsorbs organic molecules into its pores. When loaded with electron-rich oligothiophenes, the resulting system reacts under heat to initiate oxidative polymerization without the use of any other oxidant or catalyst. This reaction is not observed in the non-redox-active MOF MIL-100(Al). We have characterized the composites by optical and nanoscale microscopy, vibrational and UV-vis spectroscopy, X-ray photoelectron spectroscopy, N2 sorption analysis, and thermogravimetric analysis/residual gas analysis. Unsubstituted oligothiophenes polymerize within MOF pores, while 3,4-ethylenedioxythiophene forms a coating on the MOF surface. MOF composites with conjugated polymer dopants trapped inside their pores undergo profound shifts in the composite electronic structure. Reasoning from time-dependent density functional theory 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.

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.