As shown on Table , we obtain a bulk modulus of K crystal = 1.39 GPa, in reasonable agreement with previous experimental 24,28,33 and computational works. It is in the lower range of values (see Table ), but further interpretation is limited, as the precise value determined depends on the computational methodology and -for experiments -also on subtle differences between MOFs from different batches or on the experimental setup. However, the comparison between two different systems within the same methodology is meaningful, and we find that the ZIF-4 glasses are less soft with K glass = 2.43 ± 0.09 GPa. This new result complements a previous nanoindentation study that found that ZIF-4 melt-quenched glasses showed larger Young's modulus (E glass = 8.2 GPa) than in their parent crystalline phase (E crystal = 4.6 GPa). Interestingly, this finite strain difference approach also yields the density at zero pressure ρ 0 which is of 1.29 g cm -3 for the crystal and of 1.34 ± 0.03 g cm -3 for the glass. We note that the glass density is higher than for the crystal, as expected from pycnometric measurements (ρ glass =1.63 g cm -3 and ρ crystal = 1.50 g cm -3 ) and from a recent CO 2 physisorption study 73