Immobilization of the Polar Group into an Ultramicroporous Metal-Organic Framework Enabling Benchmark Inverse Selective CO₂/C₂H₂ Separation with Record C₂H₂ Production

One-step harvest of high-purity lighthydrocarbons without thedesorption process represents an advanced and highly efficient strategyfor the purification of target substances. The separation and purificationof acetylene (C2H2) from carbon dioxide (CO2) by CO2-selective adsorbents are urgently demandedyet are very challenging owing to their similar physicochemical properties.Here, we employ the pore chemistry strategy to adjust the pore environmentby immobilizing polar groups into an ultramicroporous metal-organicframework (MOF), achieving one-step manufacture of high-purity C2H2 from CO2/C2H2 mixtures. Embedding methyl groups into prototype stable MOF (Zn-ox-trz)not only changes the pore environment but also improves the discriminationof guest molecules. The methyl-functionalized Zn-ox-mtz thus exhibits the benchmark reverse CO2/C2H2 uptake ratio of 12.6 (123.32/9.79 cm(3) cm(-3)) and an exceptionally high equimolar CO2/C2H2 selectivity of 1064.9 at ambient conditions.Molecular simulations reveal that the synergetic effect of pore confinementand surfaces decorated with methyl groups provides high recognitionof CO2 molecules through multiple van der Waals interactions.The column breakthrough experiments suggest that Zn-ox-mtz dramatically achieved the one-step purificationcapacity of C2H2 from the CO2/C2H2 mixture with a record C2H2 productivity of 2091 mmol kg(-1), surpassing allof the CO2-selective adsorbents reported so far. In addition, Zn-ox-mtz exhibits excellent chemicalstability under different pH values of aqueous solutions (pH = 1-12).Moreover, the highly stable framework and excellent inverse selectiveCO(2)/C2H2 separation performance showcaseits promising application as a C2H2 splitterfor industrial manufacture. This work paves the way to developingreverse-selective adsorbents for the challenging gas separation process.