We use the Langmuir adsorption model ρ ads Xe (P ) in eqn. 3 to describe the adsorbed density of xenon in each material as a function of pressure. We identify the Langmuir parameters M and K for each adsorbent by fitting ρ ads Xe (P )/ρ ads to the experimentally measured, gravimetric (per mass of adsorbent) xenon adsorption data at 298 K (with the exception of MOF-505, 292 K and Ni-MOF-74, 297 K). Fig. shows the raw gravimetric xenon adsorption data and the gravimetric Langmuir model fits, all of which reasonably describe the shape formed by the data. Tab. 2 lists the identified Langmuir parameters M and K for each adsorbent, in addition to the references for the adsorption data. Finally, Fig. displays (i) the volumetric (per volume of adsorbent) xenon adsorption data, converted from the gravimetric adsorption data using ρ ads , (ii) the fitted models for the adsorbed xenon density, ρ ads Xe (P ), and (iii) the bulk gas density ρ Xe (P ). The plot shows a larger pressure range than Fig. , on a logarithmic scale, to see how the model ρ ads extrapolates to pressures larger than found in the data. Compared with the bulk xenon density at the same temperature and pressure, adsorbents achieve a much higher xenon density at lower pressures (c.a. < 40 bar), but, at higher pressures, the bulk density is greater because the skeleton of the adsorbent occupies a fraction of the space and excludes xenon adsorbates. Points show the experimentally measured xenon adsorption isotherms (at 298 K, except for MOF-505, 292 K, and Ni-MOF-74, 297 K), converted from the raw gravimetric adsorption data using ρ ads . The dashed curve shows the density of the bulk gas, ρ Xe (P ). The x's mark the optimal storage conditions (P opt , ρ ads Xe (P opt )) that we will derive later. (b) The distributions (diagonal) and correlations between (off-diagonal) the Langmuir M, Langmuir K, and density ρ ads that fully characterize the adsorbents in our model adsorbed xenon propellant storage system. 3.30 18.9 Although xenon adsorption data was also available for IRMOF-1 and PCN-12 , we omit these MOFs from our analysis because their xenon adsorption isotherms do not exhibit a plateau, preventing reliable estimation of M to extrapolate the adsorbed xenon density beyond the maximum pressure observed in the data, ca. 1 bar.