Flexible metal-organic frameworks (MOFs) such as Zn(C3H3N2) (ZIF-4) and Cu2(BBCDC) (DUT-49) show intriguing structural phase transitions when triggered by external stimuli such as temperature and gas sorption. We previously showed that the change in lattice dynamics during these phase transitions can be tracked by temperature dependent inelastic neutron scattering (INS), establishing an experimental blueprint to quantify lattice dynamics in these systems. Here we want to build up on our experience, applying our approach to a more complex system, DUT-49, which recently attracted a lot of attention due to its negative gas adsorption behaviour. We propose to measure INS as a function of CH4 pressure and temperature to quantify the role of low energy lattice dynamics in the flexibility of DUT-49.