The predominance of MOFs with high ∆H CO 2 /∆H N 2 ratio but low diffusivity ( D CO 2 µ ≲ 10 -11 m 2 /s ) has important implications. Generally, we expect that a high-performing CO 2 capture material should provide conditions under which gas adsorbents efficiently diffuse within the pores and bind strongly to the adsorption sites, even though a trade-off exists. For analyzing the impact of molecular-level diffusivity in each MOF structure at the process level, the numerical diffusivity values, D µ , are propagated via the effective mass transfer coefficient K eff in Equation . The K eff vs. D µ curves in Figure exhibit two distinct regimes: micro-porosity limited transfer, and macro-porosity limited transfer. Each value of the crystallite size R µ is associated with a characteristic threshold below which mass transfer is limited by microscopic diffusion. As a rule-of-thumb, we conclude that the larger the crystallite diameter, the stronger the impact of microscopic diffusion.