Rational Creation of the Second Xe-Matched Adsorption Site in a Covalent Organic Framework via a Digging-Patching Strategy for Simultaneously Boosting Xe Uptake and Xe/Kr Selectivity

/g. As a result, we observed a large enhancement in both Xe uptake and selectivity from 1.37 to 2.29 mmol/g and from 14.6 to 22.0. It was found that structural design by the digging (D) operation in the DP strategy functions to create dual adsorption sites for Xe, which helps to improve Xe uptake, while the patching (P) operation functions to optimize the second adsorption site with its size close to the kinetic diameters of Xe, which helps to improve Xe/Kr selectivity, finally breaking the inherent trade-off between Xe uptake and Xe/Kr selectivity. The actual Xe-Kr separation capability was further confirmed by breakthrough experiments. This work highlights a fundamental structural design of two-dimensional COFs for size-based gas separation.