Abstract
AbstractElectrically conductive metal–organic frameworks (MOFs) and MOF‐like coordination polymers are an emerging class of materials that combine good electrical charge transport with unique properties such as nanoporosity. The combination of different metal nodes and organic linkers allows tailoring MOFs to specific properties and applications in electronics, like selective chemiresistive sensing. The intrinsic crystallinity of MOFs, which usually promotes efficient charge transport, makes them also difficult to integrate into flexible systems, as crystalline MOFs are often brittle. The present study reports on a fast and reliable interfacial synthesis of conductive MOF films composed of two different organic ligands, 2,3,6,7,10,11‐hexahydroxytriphenylene (HHTP) and 7,7,8,8‐tetracyanoquinodimethane (TCNQ), lacking long‐range periodic order while preserving good electrical conductivity of 0.033 S cm−1 at room temperature and chemiresistive response toward ambient changes. The hybrid nature of the discontinuous film is investigated multiparametrically by electron and atomic force microscopy as well as by Raman spectroscopy. This study demonstrates that including different types of MOFs is a good compromise between structural order and conductivity, thus making hybrid framework architectures to a promising active material for chemiresistive sensors without the need for high crystallinity.
Highlights
Conductive metal–organic frameworks (MOFs) and MOF-like ferent building blocks, the physical and coordination polymers are an emerging class of materials that combine good electrical charge transport with unique properties such as nanoporosity
We present a fast and simple synthesis of a hybrid MOF film, composed of copper ions and two different organic ligands HHTP and TCNQ, that shows an average conductivity of 0.033 S cm−1 and a chemiresistive response toward ambient changes, despite its discontinuous architecture and its highly amorphous phase
Cu-HHTP-TCNQ hybrid films were synthesized by a biphasic system of aqueous Cu(II) nitrate solution and ethyl acetate containing dissolved HHTP and TCNQ organic ligands (Figure 1, and Experimental Section for details)
Summary
Cu-HHTP-TCNQ hybrid films were synthesized by a biphasic system of aqueous Cu(II) nitrate solution and ethyl acetate containing dissolved HHTP and TCNQ organic ligands (Figure 1, and Experimental Section for details). With a longer reaction time, the film became more opaque resulting in a clearly visible black film after 15 min, at the latest (Figure 1c). The growth of a continuous film was only initiated when both organic molecules were combined. The lateral dimension of continuously grown Cu-HHTP-TCNQ film was defined by the reaction vial, encompassing an area of about 5 cm. Mechanical stability seems to improve due to ongoing film growth because the floating film no longer broke so . Film deposition was realized by initially placing a substrate of choice on the bottom of the reaction vessel and carefully removing the liquid phases with a syringe after film growth, allowing the film to sink (Video S1, Supporting Information). Glass substrates with prepatterned gold electrodes were used (Figure 1c, inset)
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