Thermodynamic Modeling of the Selective Adsorption of Carbon Dioxide over Methane in the Mechanically Constrained Breathing MIL‐53(Cr)

Abstract

The coadsorption of CO 2 /CH 4 in the breathing MIL-53(Cr) under the application of an additional mechanical pressure is investigated through the use of an extended thermodynamic mean-field model. The focus is on the breathing behavior, negative gas adsorption (NGA), and selective adsorption of CO 2 as well as to what degree the application of mechanical pressure influences this behavior. To this end, phase diagrams, coadsorption isotherms are constructed and the CO 2 /CH 4 selectivity is computed in terms of the vapor pressure of methane and carbon dioxide as well as the mechanical pressure. As a result, it is found that NGA can be induced by coadsorption of CO 2 /CH 4 gas mixtures with certain molar compositions. Finally, a specific adsorption/desorption cycle, which includes the application of an additional mechanical pressure, is proposed to allow for an increased CO 2 /CH 4 selectivity as well as for an expected less energy demanding CO 2 desorption step.

Understanding carbon dioxide capture on metal–organic frameworks from first-principles theory: The case of MIL-53(X), with X = Fe3+, Al3+, and Cu2+

“…[12][13][14][15][16] In particular, the MIL-53 frameworks comprise an inorganic region formed by the metallic centers connecting oxygen atoms from hydroxyl groups (axial positions) or benzene dicarboxylate (BDC) ligands (equatorial positions) in an octahedral configuration. [17][18][19] In recent years, the applicability of this series has been widely evaluated by means of experimental 14,18,[20][21][22][23][24][25] and theoretical methods 17,26 for gas adsorption, including carbon dioxide, 14,18,[20][21][22][23]26,27 methane, 18,23,25,26 and hydrogen sulfide. 24 In general, the presence of open metal sites with appropriate geometry and pore size in metal-organic frameworks is directly associated with high adsorption capacity and selectivity.…”

Effect of Water and Carbon Dioxide on the Performance of Basolite Metal–Organic Frameworks for Methane Adsorption

“…From Figure A, slight reductions in methane adsorption capacity are observed for basolite C300 (0.9%) and F300 (1.1%), with even an increase of 12.4% for A100. The variation of basolite A100, which can be considered significant, can be attributed to its long pore (lp) state, which facilitates the access to active metal centers by methane . Additionally, the selectivity of basolite A100 toward carbon dioxide is not too high, and the concentration is low, leading to an increase in methane adsorption capacity.…”

Cutting-edge molecular modelling to unveil new microscopic insights into the guest-controlled flexibility of metal–organic frameworks

“…Figure 1b summarizes the flowchart of the newly developed OMD approach and its key advantages as compared to the HOMC method: i) the production of a full dynamical and ergodic trajectory and ii) the absence of homogenization between MC and MD partition functions to ensure a correct detailed balance 30 . Indeed, the reversibility of the Markov chain during the transition between MC and MD parts can be only satisfied if the MC and MD partition functions are similar The implementation of this OMD strategy is first validated on the MIL-53(Cr) a MOF that has already been intensively studied in the past by MD 29,39,40 , HOMC 30,31 , MC 20,41 and theoretical models 8,25,38 . As a further stage, the OMD scheme is trained to capture and understand in-depth the NGA phenomenon exhibited by DUT-49(Cu), by far the most complex breathing phenomenon exhibited by a MOF.…”

“…The implementation of this OMD strategy is first validated on MIL-53(Cr) a MOF that has already been intensively studied in the past using MD, 29,39,40 HOMC, 30,31 MC 20,41 and theoretical models. 8,25,38 As a further stage, the OMD scheme is trained to capture and understand in-depth the NGA phenomenon exhibited by DUT-49(Cu), by far the most complex breathing phenomenon exhibited by a MOF. The microscopic picture of the structural transition occurring during the NGA process is unprecedented and emphasizes the strength of the newly developed OMD approach to tackle the most challenging structural transition in solid state materials.…”

“…the np and op forms and the stable intermediate phases (ip), the structural transition has never been captured so far since it occurs too quickly (10-100 pico-seconds) to be experimentally detectable. 6,7,[20][21][22] Similarly, theory using thermodynamics models [23][24][25][26][27] based on free energy calculations and macroscopic formulation has been successfully implemented to predict the thermodynamic stability of these different phases depending on the gas pressure and temperature; however, their inherent limitations prevented an understanding of the physics at the origin of these phase transformations. Force eld molecular modelling offers an alternative route to deliver a full atomistic picture of such a breathing phenomenon.…”