Entropy-derived Lewis acid-base thermodynamic parameters of solid surfaces: A generalized five-parameter framework...

Adsorption entropy is a fundamental thermodynamic quantity governing molecular organization at solid surfaces, yet its physicochemical significance remains considerably less explored than adsorption enthalpy and free energy. In this work, a generalized five-parameter Lewis acid-base entropy model is proposed for the quantitative interpretation of the polar adsorption entropy of organic molecules on solid surfaces. The model introduces five entropy-derived thermodynamic parameters, ω_A, ω_D, ω, ω_2A, and ω_2D, associated with first-order acidic and basic contributions, amphoteric donor-acceptor coupling, and nonlinear second-order effects. The model was applied to adsorption entropy data obtained by inverse gas chromatography at infinite dilution (IGC-ID) for Rh/H-Beta zeolites containing 0-2 wt% rhodium, MgY and NH₄Y zeolites, and oxide surfaces including silica, ZnO, Zn, alumina, titania, and MgO. Statistical comparisons among different entropy formulations demonstrated that higher-order Lewis acid-base contributions are frequently required to accurately describe adsorption entropy. Depending on the investigated material, the optimal representation was provided by the 3-P, 4.2-P, 4.3-P, or generalized 5-P models, highlighting the importance of amphoteric and nonlinear organizational effects. A statistical thermodynamic interpretation was further developed through the introduction of an organizational statistical probability, P_org, which quantitatively relates adsorption entropy to molecular organization at solid interfaces. Strong quadratic relationships were established between adsorption entropy, entropy-derived Lewis acid-base parameters, and specific surface area, revealing highly regular structural trends across zeolites and oxides. The proposed framework establishes adsorption entropy as a powerful tool for surface characterization and provides the foundations of an Entropic Lewis Acid-Base Surface Chemistry applicable to adsorption, inverse gas chromatography, catalysis, porous materials, and interfacial phenomena.