Spatial-Electrostatic Potential Synergistically Driven in Isoreticular Metal-Organic Frameworks for Inverse CO2/C2H2 Separation.

The rational design of microporous metal-organic frameworks (MOFs) with inverse carbon dioxide (CO2) selectivity for carbon dioxide/acetylene (C2H2) separation to achieve one-step purification of C2H2 is still a challenging task. Herein, we present a spatial-electrostatic potential synergistic strategy within isoreticular MOFs (HBM-1 and HBM-2) through immobilization of functional groups to enhance inverse CO2-selective adsorption performance and achieve the ultimate goal of one-step C2H2 purification. A precise spatial design of the pore environment using a hydroxyl functional group as the pore environment regulator enabled the spatial-electrostatic potential synergistic increase in CO2 adsorption and enhanced inverse CO2/C2H2 separation performance. Based on this strategy, two new ultramicroporous isostructural MOFs were synthesized. Compared to HBM-1a, HBM-2a (HBM-1a and HBM-2a are activated HBM-1 and HBM-2, respectively) exhibited a high CO2 uptake (56.72 cm3 g-1) and CO2/C2H2 selectivity (3.4) under ambient conditions. The preferential CO2 adsorption and inverse selective adsorption mechanism was confirmed by theory calculations. The breakthrough experiments indicated that HBM-2a could efficiently separate the CO2/C2H2 mixture and possess good cycling stability. This design strategy could provide valuable insights into constructing inverse CO2-selective adsorbents to achieve one-step C2H2 purification.