Search for: All records

Electrode dissolution is the primary mode of degradation for two-dimensional metal–organic frameworks (2D cMOFs) under electrochemical polarization. Leveraging low solubility of ligands into MOF design enables long term cycling stability. 

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. 

Selectively blocking undesirable exciton transfer pathways is crucial for utilizing exciton conversion processes that involve participation of multiple chromophores. This is particularly challenging for solid-state systems, where the chromophores are fixed in close proximity. For instance, the low efficiency of solid-state triplet–triplet upconversion calls for inhibiting the parasitic singlet back-transfer without blocking the flow of triplet excitons. Here, we present a reticular chemistry strategy that inhibits the resonance energy transfer of singlet excitons. Within a pillared layer metal–organic framework (MOF), pyrene-based singlet donors are situated perpendicular to porphyrin-based acceptors. High resolution transmission electron microscopy and electron diffraction enable direct visualization of the structural relationship between donor and acceptor (D–A) chromophores within the MOF. Time-resolved photoluminescence measurements reveal that the structural and symmetry features of the MOF reduce the donor-to-acceptor singlet transfer efficiency to less than 36% compared to around 96% in the control sample, where the relative orientation of the donor and acceptor chromophores cannot be controlled.