To ascertain the value of O NMR as a probe, the 17 O NMR parameters were calculated using DFT calculations for amine appended Mg2(dobpdc) containing a wide range of organic diamines. The use of DFT calculations provides an excellent opportunity to explore and compare both known and novel adsorption products. Of the three adsorption mechanisms explored, ammonium carbamate chains, carbamic acid pairs and the mixed adsorption mechanism, four unique O environments were identified: M-OCO and M-OCO -, resulting from ammonium carbamate chains and COOH and COOH, resulting from the formation of carbamic acids. Each environment can be identified by their O NMR parameters, as shown in Table . The key distinguishing feature for carbamic acids is the lower chemical shift, large CQ and small hQ values for the OH. Furthermore, in general, the metal bound oxygen can be distinguished from the carbamate O by a lower chemical shift. These calculations suggested that O NMR spectroscopy is a powerful probe into these adsorption mechanisms. Experiments were then performed to explore this further. ammonium carbamate chains and therefore the O NMR spectroscopy confirms this binding mechanism for (ee-2)2-Mg2(dobpdc). The second amine-appended Mg2(dobpdc) material of interest is dmpn-Mg2(dobpdc). As discussed previously, dmpn-Mg2(dobpdc) is thought to capture CO2 via a mixed adsorption mechanism, however, the assignment of this binding mechanism is not conclusive by 1 H and 13 C NMR spectroscopy owing to the overlap of signals for similar C environments. Excitingly, the O MAS spectrum (Figure ) for dmpn-Mg2(dobpdc) showed a broad overlapping of multiple signals corresponding to chemisorption of CO2 and two sharp resonances corresponding to physisorbed CO2.