Solvation pressure in spherical mesopores: Macroscopic theory and molecular simulations

Abstract

Fluids adsorbing in nanoporous solids cause high solvation pressures that deform the solids and affect properties of the fluids themselves. We calculate solvation pressure of nitrogen adsorbed at 77.4 K in spherical silica mesopores using two methods: the macroscopic Derjaguin-Broekhoff-de Boer theory and molecular simulations. We show that both approaches give consistent results, and the observed pressures increase in smaller pores reaching the order of a hundred megapascals. The results are also typical for the solvation pressure in mesoporous materials, yet noticeably differ from the results for the cylindrical pore geometry. Furthermore, we show that the dependence of the solvation pressure at saturation on the reciprocal pore size is linear, and we use this relation for the calculation of the solid-liquid surface energy. The results can be employed for the prediction of the solvation pressure and the adsorption-induced deformation in the material with the spherical pore geometry.

Adsorption-Induced Deformation of Slit-Shaped Ink-Bottle Pores

“…AID in spherical pores was studied through the macroscopic thermodynamic model and GCMC simulation. The results from the two methods are consistent and similar to the deformation of the cylinder pore …”

“…The results from the two methods are consistent and similar to the deformation of the cylinder pore. 18 Despite the well-documented pore geometry dependence of AID, a typical and widely concerned pore geometry, the inkbottle pore, has not been involved. The ink-bottle pore contains wide and narrow sections, namely, the cavity and neck, respectively.…”

Density Functional Theory Model for Adsorption-Induced Deformation of Mesoporous Materials with Nonconvex Pore Geometry

“…Simple geometrical representations of pores (planar, cylindrical, or spherical) were sufficient in order to reproduce not only adsorption isotherms but also strain isotherms. 17,26,31,32 However, there is a class of materials, whose pores substantially differ from "simple" ones, namely, their porous body consists of convex, predominantly nonporous parts. Important examples are opals, the pore structure of which are formed by nonconvex pores.…”

“…Up to now, the focus in the investigations of adsorption-induced deformation has been mainly on materials with planar or convex pores, for example, templated silica or porous glasses. Simple geometrical representations of pores (planar, cylindrical, or spherical) were sufficient in order to reproduce not only adsorption isotherms but also strain isotherms. ,,, However, there is a class of materials, whose pores substantially differ from “simple” ones, namely, their porous body consists of convex, predominantly nonporous parts. Important examples are opals, the pore structure of which are formed by nonconvex pores. , Some templated carbons also have nonconvex pores and present a nice reference material for studying adsorption-induced deformation, such as inverse replica of SBA-15 silica, CMK-3 templated carbon, which consists of hexagonally ordered rods held together by thin interconnections .…”

Adsorption-Induced Deformation of Zeolites 4A and 13X: Experimental and Molecular Simulation Study

“…This model represented zeolite pores as uniform spheres of adjusted pore size to estimate the strain based on the solvation pressure, which matched experimental data . However, zeolites can exhibit anisotropy of the deformed framework , that cannot be captured within macroscopic models that consider only normal components of the stress tensor . In complex geometries, the solvation force has both significant normal and tangential components, and the distribution of the solvation force at the solid surface is nonuniform .…”