CO 2 Adsorption in Amine Functionalized Mixed Ligand Metal-organic Frameworks of UiO-66 topology

A series of mixed ligand (ML: H2-BDC/NH2-BDC) UiO-66 MOFs, synthesized via two different methods (LT, low temperature and HT, high temperature) have been investigated for their CO2 adsorption properties from 0 to 1 bar in order to clarify the role of NH2 loading on CO2 uptake. Volumetric CO2 isotherms show that the CO2 capacity (normalized to the Langmuir surface area) increases with the functionalization degree of about 46%; for similar NH2 content same values are found for both the synthesis procedures. Microcalorimetric isotherms reveal that amino-functionalized materials have a larger differential heat of adsorption (q diff ) towards CO2; respectively reaching 27 (25) and 20 (22) kJ/mol on HT(LT) UiO-66-NH2 and UiO-66 at the lowest equilibrium pressures used in this study. All experimental results are well supported by values obtained via quantum mechanical calculations.