Entropy-derived Lewis acid-base thermodynamic parameters of solid surfaces: A generalized five-parameter framework for polar adsorption entropy and molecular organization by inverse gas chromatography.

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, ωA, ωD, ω, ω2A, and ω2D, 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, Porg, 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.