Is iron unique in promoting electrical conductivity in MOFs?

Abstract

Identifying the metal ions that optimize charge transport and charge density in metal–organic frameworks is critical for systematic improvements in the electrical conductivity in these materials.

Coordination-induced reversible electrical conductivity variation in the MOF-74 analogue Fe2(DSBDC)

“…(Fig. 4), 36 as would be expected upon removal of pore-blocking DMF molecules. Although Fe 2 (DSBDC) is crystalline, its PXRD pattern diverges from those of both Fe 2 (DSBDC)(DMF) 2 ·x(DMF) and Fe 2 (DSBDC)(DMF) 2 : peaks at 6.6°and 11.3°corresponding to the [2][3][4][5][6][7][8][9][10] and [300] planes in the original regular hexagonal lattice are intact, but a new peak at 10.5°appears (Fig.…”

“…§ Electron transfer thus generates holes as charge carriers, induces effectively mixed valency in (-Fe-S-) ∞ chains, and improves charge density and electrical conductivity. 36 Conclusions DMF binding to the coordinatively unsaturated Fe centers in Fe 2 (DSBDC) leads to thousand-fold increase in the electrical conductivity at 297 K. DFT calculations identify electron transfer from Fe centers to the bound DMF molecules as a possible mechanism for improving charge density in the skeleton of the MOF. These results reinforce the importance of redoxmatching between the framework and guest molecules to achieve electrically conductive MOFs, and point out the possibility of tuning electrical conductivity via coordinating guest molecules as well as applying MOFs with open metal sites for chemiresistive sensing of coordinating molecules.…”

“…We hence conjecture that the major charge transport mechanism in activated Fe 2 (DSBDC) is hole hopping between Fe and S within the (-Fe-S-) ∞ chains, similar to the situation proposed in Fe 2 (DSBDC) (DMF) 2 . 26,36 Because the skeletons of Fe 2 (DSBDC)(DMF) 2 and the DCMsoaked Fe 2 (DSBDC) are isostructural, DMF likely does not affect charge mobility. Instead, it modulates charge density in the skeleton of the framework.…”

Electrically Conducting Nanocomposites of Carbon Nanotubes and Metal‐Organic Frameworks with Strong Interactions between the two Components

“…These are based either on the usage of specific linkers, among them compounds containing tetrathiafulvalene or other sulfur‐containing moieties, or the so‐called graphene‐analogue MOFs based on triphenylene linker molecules . Fe(II)‐based framework structures often exhibit higher conductivities than their isostructural counterparts based on other metal ions . The insertion of guest molecules into MOFs with open metal sites can also create electrical conductivity but the insertion naturally goes along with a partial loss of the porosity.…”

“…[15][16][17][18] Fe(II)-based framework structures often exhibit higher conductivities than their isostructural counterparts based on other metal ions. [19][20][21][22] The insertion of guest molecules into MOFs with open metal sites can also create electrical conductivity [23][24][25] but the insertion naturally goes along with a partial loss of the porosity.…”