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Gas separation is a very important industrial process for manufacturing chemicals, fuels, plastics, and polymers but is also energy intensive through the traditional cryogenic distillations. Adsorptive gas separation by porous materials can potentially fulfill the energy-efficient separation economy. Metal-organic frameworks (MOFs), a new generation of porous materials, have been demonstrated for their promise in addressing important gas separations. In this review, we outline the uniqueness and basic design principles of MOF chemistry for gas separation in terms of their specific pore chemistry and molecular recognition. The finely tuned micropores for the high sieving effects and immobilized functional sites on pore surfaces for specific recognition of gas molecules have enabled us to develop a variety of microporous MOFs for many gas separations with both high separation selectivity and productivity. We highlight the major progress and achievements in this very important topic, which will further facilitate the extensive research endeavors and promote their industrial implementation for gas separation.

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The pore space partition (PSP) approach has been employed to realize a novel porous MOF (FJU-90) with dual functionalities for the challenging C2H2/CO2 separation under ambient conditions. By virtue of a triangular ligand (Tripp = 2,4,6-tris­(4-pyridyl)­pyridine), the cylindrical channels in the original FJU-88 have been partitioned into uniformly interconnected pore cavities, leading to the dramatically reduced pore apertures from 12.0 × 9.4 to 5.4 × 5.1 Å2. Narrowing down the pore sizes, the resulting activated FJU-90a takes up a very large amount of C2H2 (180 cm3 g–1) but much less of CO2 (103 cm3 g–1) at 298 K and 1 bar, demonstrating it to be the best porous MOF material for this C2H2/CO2 (50%:50%) separation in terms of the C2H2 gravimetric productivity. IAST calculations, molecular modeling studies, and simulated and experimental breakthrough experiments comprehensively demonstrate that the pore space partition strategy is a very powerful approach to constructing MOFs with dual functionality for challenging gas separation.