Determining the specific surface area of Metal Organic Frameworks based on a computational approach

A novel simulation approach is proposed for the representation and calculation of the specific surface area of crystalline nanoporous materials (e.g. MOFs). In brief, the simulation box that contains the framework atoms is discretized with voxels, which are filtered based on an atomistic forcefield according to specific criteria (i.e. whether a voxel can be occupied by a gas molecule or not). This produces a phase function that represents the spatial distribution of matter in the biphasic (solid void) medium. The specific surface area is then derived by the correlation function of the phase function, a method well established for the calculation of the specific surface area of mesoporous media. The proposed methodology has the advantage of allowing the implementation of any atomic interaction potential and/or filter of choice. Thus, no assumption on the shape of the pores or even the framework atoms is in principle required (for instance non-spherical potentials including electrostatic interactions can be used). Furthermore, since the solid void interface has been determined, an attempt to simulate the monolayer coverage process was carried out and pertinent surface areas where also calculated by simply counting the number of molecules that form the monolayer. The results were validated against full GCMC adsorption isotherm simulations and were further compared with experimental data indicating the suitability and effectiveness of the proposed non-stochastic computational approach for the reliable, fast and accurate determination of the surface area of nanoporous solids. (C) 2016 Elsevier B.V. All rights reserved.