TPD study of the reversible retention of carbon dioxide over montmorillonite intercalated with polyol dendrimers

Organoclays with improved affinity towards carbon dioxide were obtained via montmorillonite intercalation with polyol and amino dendrimers having respectively hydroxyl or amino groups that act as adsorbing sites. Measurements through thermal programmed desorption (TPD) show that higher amounts of CO2 than predicted by stoichiometry were retained by polyol organoclays, suggesting that more than one CO2 molecule adsorb on each OH group. The latter displayed optimal base properties tailored for: (i) improved retention capacity of CO2 by increasing their number; (ii) easy consecutive gas release upon slight heating owing to their weak basicity. Unlike amines, polyols display sufficiently weak basicity to exert only physical interaction towards carbon dioxide molecules. The reversible CO2 adsorption–desorption equilibrium is discussed here in terms of acid–base interactions between the organoclay surface and surrounding CO2 molecules. The results obtained herein open new prospects in obtaining microporous materials able to act as lungs that fix reversibly polluting gases.