This work has demonstrated the significant power and considerations required for applying O NMR spectroscopy to the study of hydroxide-based CO 2 capture materials. Initial static DFT results suggested O NMR should provide clear diagnostic assignments of hydroxyl, carbonyl and water environments with respect to their δ iso and C Q values. Experimental results on MFU-4l and KHCO 3 -CD-MOF corroborated these results to an extent, with chemisorbed and physisorbed CO 2 and water/hydroxide readily assignable from 1D 17 O NMR spectra. However, more sophisticated MLFF-MD simulations were demonstrated as efficient and effective models for the influences of both carbonyl and hydroxyl dynamics in the spectra of the two MOFs.