Metal org. frameworks (MOFs) are cryst. materials that contain metal-ions or metal-ion clusters as nodes and org. ligands as linkers to form 1-, 2-, and 3-D structures. In addn. to their convenient modular synthesis and chem. tunability, this class of materials has been under intense investigation for gas storage and sepn. applications due to the discovery of many 3-D frameworks with high internal surface areas. Through careful selection of the ligand and metal, which control pore size / shape and MOF-adsorbate interactions, their uptake properties, such as gas selectivity, can be tuned. Despite these desirable properties there is still a bottleneck in the field assocd. with the deliberate design of materials for targeted applications. Theor. efforts focused on the development of structure and property prediction tools could be a means this end; however, exptl. validation of the tools is necessary for them to be accurately applied to as-yet-synthesized materials in the future. As such, we have carried out a comprehensive exptl. and theor. study of the CO2 adsorption properties in a well-known series of metal-org. frameworks M2(dobdc) M= Mg, Mn, Fe, Co, Ni, Cu, and Zn). In situ structural studies carried out in tandem with gas adsorption measurements have been used to identify the host-guest interactions that lead to significant differences in isosteric heats of CO2 adsorption. Neutron and X-ray powder diffraction and single crystal X-ray diffraction expts. are used to unveil the site-specific binding properties of CO2 within the materials while systematically varying both the amt. of CO2 and the temp. D. functional theory calcns. including van der Waals dispersion quant. corroborate and rationalize observations regarding intramol. CO2 angles and trends in relative geometric properties and heats of adsorption in the M2(dobdc)-CO2 adducts.