Insights into the Temperature‐Dependent “Breathing” of a Flexible Fluorinated Metal–Organic Framework

Abstract

The framework expansion and contraction upon carbon dioxide uptake was studied in a partially fluorinated metal-organic framework, FMOF-2. The results show framework expansion and contraction (breathing) as a function of pressure and temperature. Even at temperatures as low as -30 °C, two phase transitions seem to take place with a pressure step (corresponding to the second transition) that is greatly dependent on temperature. This behavior is described by the model proposed by Coudert and co-workers showing that the material seems to undergo two phase transitions that are temperature-dependent. The isosteric heats of adsorption at high pressures show a minimum that is concurrent with the region of CO(2) loadings where the second pressure step occurs. It was deduced that these lower enthalpy values are a consequence of the energy cost related to the expansion or reopening of the framework. Lastly, the large and reversible breathing behavior may be a product of the combination of the high elasticity of zinc (II) coordination and the apparent high flexibility of the V-shaped organic building block.

Flexible Metal–Organic Frameworks: Recent Advances and Potential Applications

“…Recently, photoresponsive flexible MOFs were reported, which could be utilized for sensing and targeted encapsulation applications . On the other hand, the thermal responsive rotation of aromatic rings or the movement of dangling side chains of the organic ligands, which can affect the conformation of the linker and the resulting framework dynamic behavior, have promoted the investigation of thermosensitive flexible MOFs. Some newly discovered examples of flexible MOFs based on above mentioned mechanisms have been summarized and reviewed in the articles of Fischer and co‐workers and Coudert …”

An Electrically Switchable Metal-Organic Framework

“…Currently, many emerging energy technologies including storage, separation, catalysis and batteries are not able to reach full maturity owing to limitations associated with the less than optimum properties of current materials12. Nanostructured organic-inorganic hybrid materials, including crystalline metal organic framework (MOF) architectures, comprise an important class of solid-state materials that could address many of these limitations34567891011121314151617. However, the potential of hybrid materials to solve energy and environmental needs will remain inherently constrained while manipulation of their chemical functionality and structure continues to be limited to standard pressure and temperature stimulation methods18192021.…”

Characterization of an Isostructural MOF Series of Imidazolate Frameworks Potsdam by Means of Sorption Experiments with Water Vapor

“…CO 2 not only has a smaller kinetic diameter (d K ) in principle (see Table 1), but is also kinetically more active at an experimental temperature of 273.15 K compared to N 2 at 77.4 K and therefore penetrates micropores more easily. Another reason for the better resolution of the micropore range is given due to a temperature-related flexibility of the adsorbents used, as it has often been reported for MOFs [47][48][49][50][51] as well as for IFP compounds [52,53]. However, isotherms derived from water vapor, which exhibits the smallest kinetic diameter of the selected adsorptives, allow a better insight in local phenomena.…”