The identification of two chemisorbed CO 2 environments suggests either a mixed bicarbonatecarbonate mechanism or a two-site (bi)carbonate mechanism is likely occurring. Heats of adsorption data supports this with an ambiguous crossover between mechanisms (Fig. ). Cross-polarisation (CP) MAS kinetic experiments were initially trialled, but remained inconclusive (Fig. ) and thus, we propose O NMR spectroscopy as having the potential to improve clarity of mechanistic assignments -particularly motivated by the direct impact the mechanistic difference between carbonate and bicarbonate has on material CO 2 capacity.