This constraint reflects the energetic heterogeneity of CO2 adsorption. For N2, in cases where the adsorption isotherm is linear over the pressure range, we adopt the Equal Energy Site (EES) formulation of the extended DSL model. This formulation recognises the energetic homogeneity of N2 adsorption by setting the interaction energy parameters (i.e., 𝑏 , and ∆𝐻 , ) to the same value at both sites. In cases where N2 adsorption deviates substantially from linearity, this constraint is relaxed, and the fitting protocol used to model CO2 adsorption is utilised. This approach has been validated using binary mixture GCMC simulations (see supplementary note 1.3).