Humidity-Mediated Anisotropic Proton Conductivity through the 1D Channels of Co-MOF-74

Abstract

<jats:p>Large Co-MOF-74 crystals of a few hundred micrometers were prepared by solvothermal synthesis, and their structure and morphology were characterized by scanning electron microscopy (SEM), IR, and Raman spectroscopy. The hydrothermal stability of the material up to 60 °C at 93% relative humidity was verified by temperature-dependent XRD. Proton conductivity was studied by impedance spectroscopy, using a single crystal. By varying the relative humidity (70–95%), temperature (21–60 °C), and orientation of the crystal relative to the electrical potential, it was found that proton conduction occurs predominantly through the linear, unidirectional (1D) micropore channels of Co-MOF-74, and that water molecules inside the channels are responsible for the proton mobility by a Grotthuss-type mechanism.</jats:p>

The role of sulfonate groups and hydrogen bonding in the proton conductivity of two coordination networks

“…Further conductivity values at 22 °C are plotted in Figure 3 for r.h. values between 70% and 90%. A strong impact of humidity is observed for both materials; obviously, proton conduction is strongly mediated by water, as frequently observed for similar materials [ 22 – 23 ].…”

“…As expected, both materials show an increase in conductivity with increasing temperature; this applies to samples both before and after thermal activation. The relation between conductivity and temperature can be used to estimate the activation energy E A of proton mobility by using the Arrhenius equation ( Equation 1 ), where σ 0 is a material-specific factor and k B is Boltzmann’s constant [ 22 – 24 ]:…”

Pyridine Detection Using Supramolecular Organic Frameworks Incorporating Cucurbit[10]uril

“…Empty cavities in the Q­[ n ] molecule are due to the lack of coordinated metal ions at the portals of Q­[ n ] molecules; these characteristics result in simple Q­[ n ]-based SOFs having more unique adsorption properties . Between 2007 and 2011, several Q­[ n ]-based SOFs were found to have extraordinary properties for absorbing gas in carbon dioxide and acetylene or anisotropic proton conductivity . Interactions were recorded between portal carbonyl groups, methine groups, and methylene groups (C–H···O hydrogen bonds), classified as interactions on the outer surface of Q­[ n ]­s .…”

“…21 Between 2007 and 2011, several Q[n]-based SOFs were found to have extraordinary properties for absorbing gas in carbon dioxide and acetylene 22 or anisotropic proton conductivity. 23 Interactions were recorded between portal carbonyl groups, methine groups, and methylene groups (C−H•••O hydrogen bonds), classified as interactions on the outer surface of Q[n]s. 24 By mixing ethanol with a Q [6] solution containing hydrochloride under controlled conditions, Thallapally and Tian prepared three simple Q [6]-based SOFs. Here, a simple Q [6]-based SOF form containing nanoplate particles was found to adsorb 15 wt % CO 2 at 298 K and 1 bar; this form exhibited permanent porosity, a high level of thermal stability, and the greatest specific surface area of known solid-state Q [6] forms to date.…”

First-Principles Grand-Canonical Simulations of Water Adsorption in Proton-Exchanged Zeolites

“…Importantly, under all bulk conditions examined (lowest loading of 5.5 molecules per unit cell at a relative humidity as low as 0.01), the zeolitic protons easily detach from the surface O sites and hop into adsorbed water clusters, leading to hydronium ions with a broad spatial distribution. These observations have strong implications for proton conductivity inside porous materials 67 and reactions catalyzed by acidic zeolites, such as biomass conversion in the presence of solvents and transformation of hydrocarbon feedstocks containing water impurities.…”