Brunauer–Emmett–Teller Areas from Nitrogen and Argon Isotherms Are Similar

Despite recommendations from the 2015 International Union of Pure and Applied Chemistry (IUPAC) technical report, surface areas of porous materials continue to be characterized by an N₂ adsorption isotherm using the Brunauer–Emmett–Teller (BET) method. In this study, we provide the basis for such a practice by carrying out systematic large-scale molecular simulations on homogeneous and heterogeneous model surfaces. Specifically, we investigated the purported “orientational effect” of the N₂ molecule on these surfaces. Grand canonical Monte Carlo (GCMC) simulation results from 257 diverse metal–organic frameworks show that the BET areas from Ar and N₂ are similar in the range of 250–7500 m²/g with a mean deviation of 4%. Detailed analyses based on the consistency criteria for BET equations reveal that the large deviation (>10%) between the BET areas from Ar and N₂ are materials specific and more prone to materials that are not able to satisfy the 3 and 4 consistency criteria. For materials that satisfy all four consistency criteria, the BET areas predicted from Ar and N₂ isotherms are comparable.