To assign the chemisorbed CO 2 environment a first comparison to the simple static DFT calculation was performed (Fig. ), i.e. a slow exchange regime was assumed (see Fig. ). This immediately gave the clear result that no static hydroxyl group is present in the CO 2 binding mode in CD-MOF. The calculated carbonyl environments are in broad agreement with the experimental spectrum giving two mechanistic possibilities: i) only carbonate species are present -i.e. no hydroxyl groups; ii) bicarbonate/hydroxyl groups are present but chemical exchange alters the spectrum.