title: Stress-Based Model for the Breathing of Metal-Organic Frameworks.
abstract: Gas adsorption in pores of flexible metal-organic frameworks (MOF) induces elastic deformation and structural transitions associated with stepwise expansion and contraction of the material, known as breathing transitions between large pore (lp) and narrow pore (np) phases. We present here a simple yet instructive model for the physical mechanism of this enigmatic phenomenon considering the adsorption-induced stress exerted on the material as a stimulus that triggers breathing transitions. The proposed model implies that the structural transitions in MOFs occur when the stress reaches a certain critical threshold. We showcase this model by drawing on the example of Xe adsorption in MIL-53 (Al) at 220 K, which exhibits two consecutive hysteretic breathing transitions between lp and np phases. We also propose an explanation for the experimentally observed coexistence of np and lp phases in MIL-53 materials.
authors.affiliation: Chimie ParisTech (École nationale supérieure de chimie de Paris), CNRS and Université Pierre et Marie Curie, 11 rue Pierre et Marie Curie, 75005 Paris, France.|Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, New Jersey 08854-8058.
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Neimark
authors.affiliation: Chimie ParisTech (École nationale supérieure de chimie de Paris), CNRS and Université Pierre et Marie Curie, 11 rue Pierre et Marie Curie, 75005 Paris, France.
authors.forename: François-Xavier
authors.initials: FX
authors.lastname: Coudert
authors.affiliation: Chemistry Department, École normale supérieure, 24 rue Lhomond, 75005 Paris, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Boutin
authors.affiliation: Chimie ParisTech (École nationale supérieure de chimie de Paris), CNRS and Université Pierre et Marie Curie, 11 rue Pierre et Marie Curie, 75005 Paris, France.
authors.forename: Alain H
authors.initials: AH
authors.lastname: Fuchs
keywords: MIL-53; MOF; adsorption; adsorption stress; metal−organic frameworks; structural flexibility