  In this paper, we introduce a novel, adapted approach for computing gas
adsorption properties in porous materials. We analyze the Dubinin-Polanyi's
adsorption model and investigate various frameworks to estimate its required
essential components. Those are linked to physicochemical properties of the
adsorbates, such as the vapor saturation pressure and density in the adsorbed
state. To conduct this analysis, we obtain adsorption isotherms for several
metal-organic frameworks, encompassing a range of pore sizes, shapes, and
chemical compositions. We then apply and evaluate multiple combinations of
models for saturation pressure and density.
  After the evaluation of the method, we propose a working thermodynamic model
for computing adsorption isotherms, which entails using the critical isochore
as an approximation of the saturation pressure above the critical point and
applying Hauer's method with a universal thermal expansion coefficient for
density in the adsorbed state. This framework is applicable not only to
simulated isotherms but also to experimental data from the literature for
various molecules and structures, demonstrating robust predictive capabilities
and high transferability. Our method showcases superior performance in terms of
accuracy, generalizability, and simplicity compared to existing methods
currently in use. For the first time, a method starting from a single
adsorption curve and based on physically interpretable parameters can predict
adsorption properties across a wide range of operating conditions.
