Detailed neutron powder diffraction (NPD) expts. were carried out on the parent and CO2 adsorbed Mg-MOF-74 (MOF: metal-org. framework). Data collected at low temp. revealed two CO2 adsorption sites on the pore surface and multiple changes in the framework as a function of CO2 loading. Upon heating the samples to room temp., the data revealed minimal changes in expansivity upon adsorption of up to 0.94 CO2/Mg (≈ 25% mass fraction). Further, temp.-dependent data collected on the bare framework reveals net zero thermal expansion between 10 and 475 K.