Porous lanthanide metal–organic frameworks with metallic conductivity

Abstract

Metallic charge transport and porosity appear almost mutually exclusive. Whereas metals demand large numbers of free carriers and must have minimal impurities and lattice vibrations to avoid charge scattering, the voids in porous materials limit the carrier concentration, provide ample space for impurities, and create more charge-scattering vibrations due to the size and flexibility of the lattice. No microporous material has been conclusively shown to behave as a metal. Here, we demonstrate that single crystals of the porous metal–organic framework Ln 1.5 (2,3,6,7,10,11-hexaoxytriphenylene) (Ln = La, Nd) are metallic. The materials display the highest room-temperature conductivities of all porous materials, reaching values above 1,000 S/cm. Single crystals of the compounds additionally show clear temperature-deactivated charge transport, a hallmark of a metallic material. Lastly, a structural transition consistent with charge density wave ordering, present only in metals and rare in any materials, provides additional conclusive proof of the metallic nature of the materials. Our results provide an example of a metal with porosity intrinsic to its structure. We anticipate that the combination of porosity and chemical tunability that these materials possess will provide a unique handle toward controlling the unconventional states that lie within them, such as charge density waves that we observed, or perhaps superconductivity.

Fluorine extraction from organofluorine molecules to make fluorinated clusters in yttrium MOFs

“…[16][17][18][19] There is growing interest in rareearth (RE) MOFs, particularly due to their high coordination number (CN: 6-12), magnetic properties, optical properties, and therapeutic applications. [20][21][22][23][24][25] The RE metal ions tend to form dimers that oen result in MOFs with low porosity. [26][27][28] It has been widely reported that the addition of a modulator can result in RE-MOFs with larger metal clusters.…”

“…Metal–organic frameworks (MOFs) are crystalline hybrid organic–inorganic compounds that have been used in a variety of applications including conductive materials, 1–3 catalysis, 4–9 drug delivery, 10 radio therapy, 11–13 water harvesting, 14,15 gas storage, and separations. 16–19 There is growing interest in rare-earth (RE) MOFs, particularly due to their high coordination number (CN: 6–12), magnetic properties, optical properties, and therapeutic applications.…”

Ligand-Mediated Hydrogenic Defects in Two-Dimensional Electrically Conductive Metal–Organic Frameworks

“…However, there is a subset of electrically conducting scaffolds that show promise for applications in energy storage technologies, − as sensors, − and in electrocatalysis. − The most conductive examples are two-dimensional (2D)-connected (van der Waals (vdW)-stacked) and are generally thought to conduct in the out-of-plane direction (i.e., delocalizing charge through the intramolecular π-stack). Effort has been invested in designing MOF conductors with “through-space” or “through-bond” charge carrying pathways, , but the isolation of ordered 2D vdW single crystals is evasive. − The charge carrier identity and concentrations are also generally not known for the 2D conductive MOFs, and the sample-to-sample variability in electrical resistivity may be due to low carrier density, structural defects, or other types of chemical imperfections.…”

Experimental Manifestation of Redox-Conductivity in Metal-Organic Frameworks and its Implication for Semiconductor/Insulator Switching

“…1 Based on these principles, MOFs with different conductivity properties, ranging from semiconductors to metal analogues, have been obtained. [6][7][8] For example, 2D cobalt/iron 2,3,6,7,10,11triphenylenehexathiolate MOFs exhibit metallic-like character at certain temperatures as a result of strong band dispersion where a fixed level of conductivity would be expected over the applied voltage (Fig. 1a, the representative MOF is shown in Fig.…”