LTA zeolites can be synthesized with tailored adsorption properties by controlling the At content in the framework. In this work, we have demonstrated that it is possible to adjust the polarity of the zeolitic adsorbent to optimize its thermodynamic adsorption properties for the energetically relevant CO2/CH4 Separation process. The thermodynamic study has been made from the corresponding adsorption isotherms of the pure gases carried out at different pressures and temperatures, as well as breakthrough separation experiments of CO2/CH4 mixtures and the results were compared to those reported oil MOFs. The separation values obtained allow us to conclude that LTA zeolites offer unique possibilities for CH4 upgrading from natural gas.