Thermodynamic characterization of Lewis acid–base interactions on carbon nanomaterials: Validation and Universality of the Hamieh five-parameter model

Abstract

Understanding the Lewis acid–base properties of carbon materials is essential for predicting adsorption behavior, catalytic performance, and interfacial interactions. In this work, eight carbon materials—graphene, graphene oxide, reduced graphene oxide, untreated carbon fiber, oxidized carbon fiber, carbon nanotubes, carbon nanofibers, and multi-walled carbon nanotubes were investigated by inverse gas chromatography at infinite dilution over 313–383 K using nineteen probe molecules to determine the polar contribution to adsorption free energy and related thermodynamic functions. Lewis acid–base parameters were quantified using the Hamieh five-parameter adsorption model, extending classical donor–acceptor approaches through inclusion of amphoteric coupling and nonlinear effects. Comparative statistical analysis of two-, three-, four-, and five-parameter models demonstrates the superior accuracy of the five-parameter formulation, as evidenced by improved R², RMSE, AIC, and BIC values. The results reveal significant variations in Lewis acidity and basicity across materials, governed by electronic structure, defect density, and surface functional groups. Graphene exhibits dominant acidity, whereas oxidized fibers and nanotube-based materials show enhanced basicity. The observed correlations between Lewis parameters and specific surface area highlight the combined influence of electronic structure and surface topology. Overall, a unified thermodynamic framework for describing Lewis acid–base interactions on carbon nanomaterials is established.