Carbon Dioxide Adsorption in Amine‐Functionalized Mixed‐Ligand Metal–Organic Frameworks of UiO‐66 Topology

Abstract A series of mixed‐ligand [1,4‐benzenedicarboxylic acid (BDC)/2‐amino‐1,4‐benzenedicarboxylic acid (ABDC)] UiO‐66 metal–organic frameworks (MOFs) synthesized through two different methods (low (LT) and high temperature (HT)) have been investigated for their carbon dioxide adsorption properties from 0 to 1 bar to clarify the role of amino loading on carbon dioxide uptake. Volumetric CO 2 isotherms show that the CO 2 capacity (normalized to the Langmuir surface area) increases with a degree of functionalization of about 46 %; for similar NH 2 contents, the same values are found for both synthetic procedures. Microcalorimetric isotherms reveal that amino‐functionalized materials have a larger differential heat of adsorption ( q diff ) towards CO 2 ; reaching 27(25) and 20(22) kJ mol −1 on HT(LT)‐UiO‐66‐NH 2 and UiO‐66, respectively, at the lowest equilibrium pressures used in this study. All experimental results are supported by values obtained through quantum mechanical calculations.