Here, n exc. is the quantity of excess gas molecules, n abs. is the absolute total quantity of gas molecules in the adsorbent system, V p is the pore volume, and ρ exp. H 2 is the experimental hydrogen density at the same temperature and pressure as the adsorbent system. In our calculations, we used the NIST database to obtain hydrogen gas densities. A major pitfall to excess uptakes is it fails to take into account the space contribution of the adsorbent itself, which makes the adsorbent appear to be more promising. A positive excess uptake may still result in a worse performance than an tank full of hydrogen alone at the same pressure.