We seek to develop new stable MOFs for practical separation and storage of CO2 and light hydrocarbons and request 3 days on WISH to study the preferred binding sites of adsorbed gas molecules (CO2 and C2D2-4) within two related MOFs (MFM-305 and MFM-305-deCH3). The role of the –CH3 functional group on guest binding has been very rarely characterised experimentally, not least because of the invisibility of the protons by X-ray experiments. The high resolution, low background and large d-spacing capabilities of WISH make it ideal for analysing the precise locations of gas molecules within these porous MOFs and to define the preferred orientations of molecules with respect to the binding sites (i.e.,–CD3) on the pore surface. This study will reveal key structural insights into the exciting gas adsorption of these MOFs.