The dosing of enriched CO 2 on MFU-4l and CD-MOF samples was performed using the same procedure and setup for ex -situ rotor dosing previously described, using 3.2 mm or 4 mm MAS rotors. In the procedure, the MAS rotor is packed and then placed onto a custom-built vacuum/dosing line with the rotor cap resting (but not inserted) at the mouth of the rotor. The sample and gas line were evacuated for 10-15 mins, then enriched CO 2 gas is released into the evacuated line to dose the sample. Sample dosing pressures were between 0.7-1.3 bar with dosing performed for 10-30 mins to allow for gas adsorption equilibration, i.e. until no further pressure drop was observed. A plunger is then used to secure the cap and seal the rotor under the pure CO 2 environment, before removing to perform NMR measurements. Figure : Structures used for the hydrated bicarbonate anion clusters used to calculate NMR parameters given in Fig. . Energies for each cluster are given in kJ mol -1 relative to the ground state configuration, as calculated using the 6-311+G(d,p) basis set (aug-pcSseg-2 values are given in brackets). Structures are in agreement with the literature, with variations in energy ordering seen with basis set and functional choice, with relative energy fluctuation to literature of ±2 -3 kJ/mol. Figure : Structures used for the hydrated bicarbonate anion clusters used to calculate NMR parameters given in Fig. . For 5w, energies for each cluster are given in kJ mol -1 relative to the ground state configuration, as calculated using the 6-311+G(d,p) basis set (aug-pcSseg-2 values are given in brackets). For 1-4w, no additional structures were found within 2.6 kJ mol -1 of the ground state. Structures for 1-4w agree with literature, 47,50 however, for 5w a variety of structures were found to contrast to the ground state published in Reference [50] 50 with structure search unable to find the proposed minimum. This discrepancy is attributed to differing calculation methodologies. A ramped matching pulse from 90-100% was used on the proton channel). T HC = 2.4 ± 0.2 ms and 2.1 ± 0.1 ms for the the 159 and 163 ppm peaks, respectively. These cross-polarisation build up rates fit in the expected range of non-directly hydrogen bound carbon environments of T CH = 0.5 -3 ms. The similar T CH values indicate a similar type of hydrogen environment and similar carbon species, however, the possibility of a labile, dynamic hydroxyl group of a bicarbonate species and a strongly hydrogen bonded carbonate species cannot be fully distinguished by CP alone (especially given the large number of protons in the CD system). environment are identifiable when compared to the high-resolution 1D projection (Fig. ).