Cooperative Sorption on Porous Materials.

Area of Science:

• Physical Chemistry
• Materials Science
• Surface Science

Background:

• Sorption isotherm shape reflects molecular interactions, but understanding mechanisms from isotherms is challenging.
• Existing models often require assumptions about adsorption sites, layers, or pore geometry.

Purpose of the Study:

• To bridge the gap between statistical thermodynamic theory and experimental sorption isotherm analysis.
• To develop a generalized isotherm applicable to microporous and mesoporous materials.
• To reveal key system attributes controlling sorption behavior.

Main Methods:

• Derivation of a cooperative isotherm based on a statistical thermodynamic approach to interfaces.
• Utilizing sorbate-interface distribution and sorbate number distributions.
• Avoiding assumptions on adsorption sites, layers, and pore geometry.

Main Results:

• The derived cooperative isotherm generalizes existing models like the Hill isotherm.
• It directly analyzes experimental data to reveal system attributes.
• Key attributes include the cooperative number of sorbates and free energy of transfer.
• Sorbate-sorbate interactions are quantified using Kirkwood-Buff integrals.

Conclusions:

• The cooperative isotherm provides a rigorous link between sorption isotherms and molecular interactions.
• It offers a model-independent approach to understanding sorption mechanisms in porous materials.
• This method facilitates direct interpretation of experimental data to determine fundamental system properties.