Our mathematical model and the conclusions we extract from it are subject to several limitations emanating from simplifying model assumptions. We discuss some of these below. The safety factor. The choice of the safety factor influences the comparison between adsorbents and between adsorbed and bulk storage systems (see eqns. 5 and 11) because it scales the contribution to the tankage fraction by the metal composing the vessel walls. We crudely investigated the sensitivity of our results to β: only when β ≈ 0.05 does the tankage fraction of MOF-505 compete with the bulk storage system. For this very low β, only CC3 and HKUST-1 switch rankings, indicating the ranking of adsorbents here is insensitive to the choice of the safety factor β.