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, The model presented here is not tied to Langmuir fits but could be used with any analytical expression for the isotherms

, While the exact value of the maximum reached for P2 is sensitive to the uncertainties of the parameters used to describe CH4 adsorption in the np structure, we have confirmed the nonmonotonic behavior of P2(xCO2), and thus the existence of the maximum itself, well beyond the range of uncertainty in the parameters (see Fig