We refer to the BGCMC simulation as providing a "high-fidelity" estimate of the Xe/Kr selectivity of a COF, but only relative to the lower -fidelity Henry coefficient calculation. First, arguably, the high-fidelity measurement of the adsorptive Xe/Kr selectivity of a COF constitutes synthesizing and characterizing it in the lab, then taking mixedgas adsorption measurements. 113 Second, even higher-fidelity simulations of Xe/Kr adsorption are possible by (i) calculating the potential energy of a configuration E = E(n, R (n) ) using a machine learning model trained on energy calculations based on a higher level of theory (e.g. density functional theory), (ii) modeling the flexibility of the COF, 116 and/or (iii) modeling crystalline defects in the COF, 117 etc. If "high-fidelity" instead refers to performance in the real-world application, we must also consider competing adsorbates such as CO 2 and H 2 O as well as other objectives such as stability, 118,119 thermal conductivity, 120 and adsorption kinetics. 121