Realization of ideal molecular sieves, in which the larger gas molecules are completely blocked without sacrificing high adsorption capacities of the preferred smaller gas molecules, can significantly reduce energy costs for gas separation and purification and thus facilitate a possible technological transformation from the traditional energy-intensive cryogenic distillation to the energy-efficient, adsorbent-based separation and purification in the future. Although extensive research endeavors are pursued to target ideal molecular sieves among diverse porous materials, over the past several decades, ideal molecular sieves for the separation and purification of light hydrocarbons are rarely realized. Herein, an ideal porous material, SIFSIX-14-Cu-i (also termed as UTSA-200), is reported with ultrafine tuning of pore size (3.4 Å) to effectively block ethylene (C H ) molecules but to take up a record-high amount of acetylene (C H , 58 cm cm under 0.01 bar and 298 K). The material therefore sets up new benchmarks for both the adsorption capacity and selectivity, and thus provides a record purification capacity for the removal of trace C H from C H with 1.18 mmol g C H uptake capacity from a 1/99 C H /C H mixture to produce 99.9999% pure C H (much higher than the acceptable purity of 99.996% for polymer-grade C H ), as demonstrated by experimental breakthrough curves.

The separation of carbon dioxide (CO) from hydrocarbons is a critical process for the production of clean energy and high-purity chemicals. Adsorption based on molecular sieving is an energy-saving separation process; however, most of molecular sieves with narrow and straight pore channels exhibit low CO uptake capacity. Here, we report that a twofold interpenetrated copper coordination network with a consecutive pocket-like pore structure, namely, SIFSIX-14-Cu-i (SIFSIX = hexafluorosilicate, 14 = 4,4'-azopyridine, i = interpenetrated) is a remarkable CO/CH molecular sieving adsorbent which completely blocks the larger CH molecule with unprecedented selectivity, whereas it has excellent CO uptake (172.7 cm/cm) under the ambient condition. The exceptional separation performance of SIFSIX-14-Cu-i is attributed to its unique pore shape and functional pore surface, which combine a contracted pore window (3.4 Å) and a relatively large pore cavity decorated with high density of inorganic anions. Dispersion-corrected density functional theory calculation and neutron powder diffraction were performed to understand the CO binding sites. The practical feasibility of SIFSIX-14-Cu-i for CO/CH mixtures separation was validated by experimental breakthrough tests. This study not only demonstrates the great potential of SIFSIX-14-Cu-i for CO separation but also provides important clues for other gas separations.

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A highly stable amino-coordinated metal-organic framework ZJU-198 has been synthesized and structurally characterized, exhibiting high CO uptake of 105.8 cm cm while blocking off N adsorption at 1.0 bar and 298 K, attributed to the unique pore window sizes.