Insulator-to-metal-like transition in thin films of a biological metal-organic framework

Abstract

Temperature-induced insulator-to-metal transitions (IMTs) where the electrical resistivity can be altered by over tens of orders of magnitude are most often accompanied by structural phase transition in the system. Here, we demonstrate an insulator-to-metal-like transition (IMLT) at 333 K in thin films of a biological metal-organic framework (bio-MOF) which was generated upon an extended coordination of the cystine (dimer of amino acid cysteine) ligand with cupric ion (spin-1/2 system) – without appreciable change in the structure. Bio-MOFs are crystalline porous solids and a subclass of conventional MOFs where physiological functionalities of bio-molecular ligands along with the structural diversity can primarily be utilized for various biomedical applications. MOFs are usually electrical insulators (so as our expectation with bio-MOFs) and can be bestowed with reasonable electrical conductivity by the design. This discovery of electronically driven IMLT opens new opportunities for bio-MOFs, to emerge as strongly correlated reticular materials with thin film device functionalities.

Leveraging metal node-linker self-assembly to access functional anisotropy of zirconium-based MOF-on-MOF epitaxial heterostructure thin films

“…12 It is realized that for real-time applications ( e.g. membranes for gas and ion separation, electrode materials, and electronics), 13–17 stability, processibility and functional complexity of the MOFs are necessary. Stability refers to thermal, hydrolytic, and wide pH range; processibility insinuates the fabrication of large area thin films, and functional complexity means the spatial control over the functionality (porosity and polarity).…”

Ag Nanoparticles-Induced Metallic Conductivity in Thin Films of 2D Metal–Organic Framework Cu3(HHTP)2

“…The interface models were constructed by stacking pristine Cu 3 (HHTP) 2 and CuTCNQ along the [001] direction of the Ag surface (Figures S18 and S19). The total density of states (DOS) plot obtained for the pristine Cu 3 (HHTP) 2 showed a metal-like electronic band structure, evidenced by the nonzero density of states at the Fermi level, E F (can also be assigned as Mott-like), 42 although there was a distinct discontinuity between the valence band (VB) and the conduction band (CB) regions (Figure 5a), implying its semiconducting transport behavior, as was also reflected by the temperature-dependent I−V plots obtained experimentally. Interestingly, under the influence of Ag, the Cu 3 (HHTP) 2 /Ag interface resulted in a significant dispersion of the electronic band structure of Cu 3 (HHTP) 2 , altering the density of states around the Fermi level (Figure 5b).…”