Investigation of the Water Adsorption Properties and Structural Stability of MIL-100(Fe) with Different Anions

Abstract

Investigating metal-organic frameworks (MOFs) as water adsorbents has drawn increasing attention for their potential in energy-related applications such as water production and heat transformation. A specific MOF, MIL-100(Fe), is of particular interest for its large adsorption capacity with the occurrence of water condensation at a relatively low partial pressure. In the synthesis of MIL-100(Fe), depending on the reactants, structures with varying anion terminals (e.g., F, Cl, or OH) on the metal trimer have been reported. In this study, we employed molecular simulations and density functional theory calculations for investigating the water adsorption behaviors and the relative structural stability of MIL-100(Fe) with different anions. We also proposed a possible defective structure and explored its water adsorption properties. The results of this study are in good agreement with the experimental measurements and are in support of the observations reported in the literature. Understanding the spatial configurations and energetics of water molecules in these materials has also shed light on their adsorption mechanism at the atomic level.

Monte Carlo simulations for water adsorption in porous materials: Best practices and new insights

“…The adsorption and desorption branches are shown with filled and empty circles, respectively, while the NVT + W results are shown with solid lines has been a considerable discrepancy in the saturation pressure various researchers have used. Some authors have used the experimental saturation pressure, 32,33 some have used the so-called "corrected" saturation pressure [34][35][36]38 while others have used the "uncorrected" saturation pressure. [39][40][41] Some conclusions are not affected by this choice, for example, if the same water model were used in different simulations with the objective of finding the relative hydrophilicity/ hydrophobicity of materials.…”

“…Thus, it can significantly affect the predicted deliverable capacity and the resulting choice of adsorbents for a particular application. To date, some studies have used experimental saturation pressures, 32,33 while others have used the socalled "corrected" saturation pressures as proposed by Horn et al [34][35][36][37][38] The rationale behind the corrected saturation pressures is that the free energy for the simulated system requires certain analytical corrections to match the experimental free energies. Yet, others have used saturation pressures corresponding to the simulated vapor-liquid equilibrium for the particular water model used without applying the analytical corrections to match experimental data as mentioned above (referred to as "uncorrected pressures" in this work).…”

Tunable Metal–Organic Frameworks for Heat Transformation Applications

“…As a result, the adsorption for MIL-100-SO 4 begins at a lower pressure than for MIL-100-Cl. Monte Carlo simulations in a grand canonical ensemble (GCMC) were carried out to confirm the influence of the three anions in the MIL-100(Fe) structures (e.g., F−, Cl−, or OH−) for water adsorption isotherms [ 83 ]. In the simulations, the water adsorption behavior and the relative structural stability of MIL-100(Fe) were investigated.…”

Tunable Metal-Organic Frameworks for Heat Transformation Applications

“…Monte Carlo simulations in a grand canonical ensemble (GCMC) were carried out to confirm the influence of the three anions in the MIL-100(Fe) structures (e.g., F−, Cl−, or OH−) for water adsorption isotherms. [73] In the simulations, the water adsorption behavior and the relative structural stability of MIL-100(Fe) were investigated. The small cages, which provide a stronger interaction with water molecules compared to the large cages, were completely filled with water at a notably lower pressure.…”