(350c) Adsorption-Induced Deformation of Faujasite Zeolites: Molecular Simulation Study

Adsorption-induced deformation is a phenomenon of contraction or expansion of solids caused by adsorption of gases [1]. Deformation in microporous materials is especially peculiar, and the adsorption strain isotherms may even qualitatively differ for the two close pore sizes. In these cases, when the adsorption isotherms for two materials are very close, but the strain isotherms measured during progressing adsorption exhibit very different behavior, measuring the adsorption-induced deformation can be an additional tool for the characterization of nanoporous materials [2].

Additionally, adsorption-induced deformation of some materials, such as zeolites, can influence significantly their performance in many technological processes: the adsorption-induced stress can change the permeability of zeolite membranes and thus influences the efficiency of molecular-sieve separation of adsorbed fluids [3]. Therefore, understanding of relationships between framework deformations and progressing adsorption in detail is important for the development of zeolite membranes.

In recent years there was significant progress in modeling of adsorption-induced deformation. In particular, a thermodynamic model of Ravikovitch and Neimark [4] provided the predictions of strains induced by adsorption of noble gases in CaNaX zeolite, which matched the experimental measurements quite well. This model represented the zeolite pores as uniform spheres, and predicted the strain based on the solvation pressure calculated for the rigid pore. Here we revisit the problem of adsorption-induced deformation of zeolites, modeling the zeolite structure using all-atom representation. We simulate adsorption-induced deformation using a combination of the grand canonical Monte Carlo (GCMC) and molecular dynamics simulations (MD), following the approach from [5] to study adsorption-induced deformation of these materials. We showed the overall consistency between the two models.

[1] G. Y. Gor et al., Appl. Phys. Rev., 4 (2017) 011303. [2] D. W. Siderius et al., Adsorption, 23 (2017) 593. [3] T. Bowen et al., J. Membrane Sci., 245 (2004) 1. [4] P. I. Ravikovitch and A. V. Neimark, Langmuir, 22 (2006) 10864. [5] S. M. Rogge et al., Adv. Theory Simul., (2019) 1800177.