Table Negative thermal expansion coefficients (-α, where the subscripts refer to the volume and the cell lengths) of the MOFs calculated in the temperature range 40-400 K and for a reference volume and cell parameters at 100 K Interestingly, there appears to be a correlation between the porosity features of the MOFs and the magnitude of NTE, Figure , suggesting the use of large pores and high levels of porosity as one way to design new and exceptional NTE materials. This was previously observed for studies of NTE in a series of isoreticular MOFs (pcu topology), however, here we find it occurs across different topologies, although the network certainly influences NTE, as observed for the comparison of DUT-49 and PCN-68 and reported by Bouëssel du Bourg et al. for other MOF structures. This relationship mirrors previous studies in Cd(CN) 2 frameworks, which showed that guest molecules within the framework can reduce NTE and even produce positive expansion. Recently, Schneider et al. reported on a similar phenomenon in the MOF HKUST-1, whereby infiltration with TCNQ reduces NTE. Large empty cavities provide the open space for transverse vibrational modes often responsible for NTE behavior. We suggest that large empty cavities can accommodate larger amplitude vibrations, thereby producing a greater degree of NTE.