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On the Thermodynamics of Framework Breathing: A Free Energy Model for Gas Adsorption in MIL-53
- Source :
- The Journal of Physical Chemistry C
- Publication Year :
- 2013
- Publisher :
- American Chemical Society (ACS), 2013.
-
Abstract
- When adsorbing guest molecules, the porous metal-organic framework MIL-53(Cr) may vary its cell parameters drastically while retaining its crystallinity. A first approach to the thermodynamic analysis of this "framework breathing" consists of comparing the osmotic potential in two distinct shapes only (large-pore and narrow-pore). In this paper, we propose a generic parametrized free energy model including three contributions: host free energy, guest-guest interactions, and host-guest interaction. Free energy landscapes may now be constructed scanning all shapes and any adsorbed amount of guest molecules. This allows us to determine which shapes are the most stable states for arbitrary combinations of experimental control parameters, such as the adsorbing gas chemical potential, the external pressure, and the temperature. The new model correctly reproduces the structural transitions along the CO2 and CH4 isotherms. Moreover, our model successfully explains the adsorption versus desorption hysteresis as a consequence of the creation, stabilization, destabilization, and disappearance of a second free energy minimum under the assumptions of a first-order phase transition and collective behavior. Our general thermodynamic description allows us to decouple the gas chemical potential μ and mechanical pressure P as two independent thermodynamic variables and predict the complete (μ, P) phase diagram for CO2 adsorption in MIL-53(Cr). The free energy model proposed here is an important step toward a general thermodynamics description of flexible metal-organic frameworks. © 2013 American Chemical Society.
- Subjects :
- Chemistry
Thermodynamics
02 engineering and technology
010402 general chemistry
021001 nanoscience & nanotechnology
01 natural sciences
0104 chemical sciences
Surfaces, Coatings and Films
Electronic, Optical and Magnetic Materials
Hysteresis
Crystallinity
General Energy
Adsorption
Desorption
Selective adsorption
Molecule
Metal-organic framework
Physical and Theoretical Chemistry
0210 nano-technology
Porosity
Subjects
Details
- ISSN :
- 19327455 and 19327447
- Volume :
- 117
- Database :
- OpenAIRE
- Journal :
- The Journal of Physical Chemistry C
- Accession number :
- edsair.doi.dedup.....05cb9e911cb939ed71c0c260e0205d0b