Engineering Anion‐Pillared Metal–Organic Frameworks for Record Acetylene/Methane Separation.

The realization of ideal molecular sieves has a great potential to achieve the desired gas separations by fine‐tuning pore structures to generate suitable aperture sizes, which can be exclusive to larger molecules thus performing efficient separations. Despite numerous attempts, there are few developed porous materials that implement molecular sieving for C2H2/CH4 separation. Herein, we show how fine‐tuning of pore size in a series of selected SIFSIX materials achieves ideal molecular sieving for C2H2/CH4 separation at ambient conditions. With an optimized pore size of 3.4 Å and abundant binding sites in the channels, UTSA‐200 shows complete exclusion of larger CH4 molecules, while maintaining strong affinities toward C2H2. Therefore, this material exhibits both high uptake capacity at low pressure (up to 41 cm3 g−1 at 0.01 bar and 296 K) and record C2H2/CH4 selectivity (over 1×107). Dynamic breakthrough experiments validated the ideal sieving separation performance of UTSA‐200 for C2H2/CH4 mixtures, affording an exceptionally high C2H2 capacity of 73.5 L kg−1 with high purity of 99.5 % per cycle. [ABSTRACT FROM AUTHOR]