The
breathing behavior of the MIL-53(Cr) metal–organic framework
(MOF) has been explored previously upon guest-adsorption and thermal
and mechanical stimuli. Here, advanced molecular simulations based
on the use of an accurate force field to describe the flexibility
of this porous framework demonstrate that the application of an electrical
field induces the structural switching of this MOF leading to a first-order
transition and a volume change of more than 40%. This motivated us
to electrically tune the pore size of MIL-53(Cr) with the idea to
propose a new concept to selectively capture CO2 over CH4 via a molecular sieving that paves the way toward the optimization
of current separation-based processes.
This paper reports on the comparison of three zirconium-based metal organic frameworks (MOFs) for the capture of carbon dioxide and ethanol vapour at ambient conditions. In terms of efficiency, two parameters were evaluated by experimental and modeling means, namely the nature of the ligands and the size of the cavities. We demonstrated that amongst three Zr-based MOFs, MIP-202 has the highest affinity for CO2 (−50 kJ·mol−1 at low coverage against around −20 kJ·mol−1 for MOF-801 and Muc Zr MOF), which could be related to the presence of amino functions borne by its aspartic acid ligands as well as the presence of extra-framework anions. On the other side, regardless of the ligand size, these three materials were able to adsorb similar amounts of carbon dioxide at 1 atm (between 2 and 2.5 µmol·m−2 at 298 K). These experimental findings were consistent with modeling studies, despite chemisorption effects, which could not be taken into consideration by classical Monte Carlo simulations. Ethanol adsorption confirmed these results, higher enthalpies being found at low coverage for the three materials because of stronger van der Waals interactions. Two distinct sorption processes were proposed in the case of MIP-202 to explain the shape of the enthalpic profiles.
In the title compound, C5H7N5S·H2O, the main molecule is approximately planar, with a maximum deviation from the mean plane through the non-H atoms of 0.1478 (12) Å for the amine N atom. In the crystal, the components are connected via N—H⋯O, N—H⋯S and O—H⋯N hydrogen bonds, forming a three-dimensional network.
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