Metal-organic framework materials are a topical family of nanoporous solids that have potential applications in molecular storage, separation and catalysis. Some of these materials show dramatic expansion and contraction in the solid state whilst maintaining crystallinity, and this may be brought about by the choice of guest molecules or simply a change in temperature. Although crystal structures are available at different temperatures the mechanism of this flexibility is as yet unknown: this proposal aims at understanding this unusual behaviour by using RMC analysis of total scattering data. This approach has successfully been applied to other 3D structures but not yet to the highly flexible MOFs, and should yield valuable new information concerning their potential applications in molecular separation and storage.