Owing to the tuneable nature of metal-organic frameworks (MOFs), functionalisation is a common methodology employed to introduce active groups to the material for enhanced gas sorption and selectivity. The direct role of a methoxy (-OCH3) group is explored by comparing MFM-300(InOMe) to the non-functionalised, isostructural parent MFM-300(In) material. Investigating how such functional groups interact with adsorbed gas at the atomic level is fundamental for understanding the host-guest interactions and the use of MOFs for practical applications. This proposed INS study will investigate the dynamics of methoxy functional group in MFM-300(InOMe) and the changes it exhibits upon loading of acidic gas. The proposed study aims to reveal the full nature of methoxy behaviour in an ordered crystalline system, focussing on rotation modes and how these may change upon different gas loading.