Nanochannel Mediated Electrical and Photoconductivity of Metal Organic Nanotubes

Abstract

The structural features of metal−organic frameworks (MOFs) are very tempting and have proven themselves to be promising candidates for different applications such as gas storage and separation, catalysis, sensing, magnetism, drug delivery, and so forth. The nanotubular structure of MOFs leads to a new class called metal− organic nanotubes (MONTs), which are structurally analogous to carbon nanotubes. Herein, we explored the electrical conductivity and photoconductivity of two isostructural MONTs, [Zn 3 (btc) ). Solvent activation, followed by thermal activation of Zn−Zn-btc and Zn−Ni-btc MOFs result in an increase of electrical conductivity by 3 and 2 orders, respectively. The remarkable increment in conductivity after evacuating the porous channels marks the significance of MONTs. The electrical conductivity of Zn− Zn-btc is 100 times higher than that of Zn−Ni-btc despite the fact that both are isostructural. The lower conductivity of Zn−Ni-btc is attributed to the low charge carrier density and mobility due to atomic mismatch. Zn−Ni-btc displays a decrease in conductivity with increasing temperature (above room temperature), which then starts to increase after 373 K, showing lattice vibration-mediated transport below 373 K and hopping-mediated electrical transport above 373 K. Whereas Zn−Zn-btc shows a continuous decrease in conductivity with temperature mainly due to the phonon-mediated transport mechanism. Both the compounds show a photoconductivity effect at room temperature. The blue light-induced photoconductivity of Zn−Ni-btc is almost 14% higher than that of Zn−Zn-btc. The photoswitching effect is shown by both the MONTs.

Influence of Molecular Separation on Through‐Space Intervalence Transient Charge Transfer in Metal–Organic Frameworks with Cofacially arranged Redox Pairs

“…14 cm 2 V −1 s −1 ). As the charge carrier density is approximately the same in both systems, it must have been arising due to lower spacing between co‐facially oriented DPTTZ ligands in MOF 2 , which led to higher IVCT due to effective overlap of frontier orbitals at the optimum spatial arrangement of redox‐active components and thus we observed higher mobility in MOF 2 [7e,11a,12c,22a,c] . The OPTP measurements are well in accordance with the TA spectroscopy results (Figure 3), which clearly show slower growth and recovery (Tables S9–S10) of mobility trace for MOF 1 in contrast to that of MOF 2 .…”

Ultrathin MOF nanosheets and their mixed-matrix membranes for ammonia and aliphatic amine sensing in water

“…Additionally, a broad absorbance peak around 400 nm and 550 nm was observed, indicating Ni d–d transitions. 37 Fig. S4† displays the nitrogen sorption isotherm of Ni- btc NS with a Brunauer–Emmett–Teller (BET) surface area of 39 m 2 g −1 .…”

Highly active ZIF-8@CNT composite catalysts as cathode materials for anion exchange membrane fuel cells

“…31 Additionally, metal-organic frameworks (MOFs) have significant advantages in catalyst tuning and structure optimization and their derivatives usually have highly dispersed accessible active sites, improved charge transfer networks, and high porosity for efficient mass transfer of reactants. [31][32][33] Zeolitic imidazolate framework-8 (ZIF-8), as a branch of MOFs, has gained much attention as a template for preparing carbon-based catalysts due to its hierarchical porosity, high nitrogen content, excellent thermal and electrochemical stability, and volatile characteristics of Zn at higher temperatures. 34,35 This further enhances doping of nitrogen in the carbon skeleton, which changes the charge distribution and helps O 2 adsorption on the active sites.…”