Enhanced C2H2/CO2 separation in tetranuclear Cu(II) cluster-based metal-organic frameworks by adjusting divider length of pore space partition

Achieving efficient adsorption and separation of C2H2/CO2 mixtures is a goal that people have always pursued to improve the situation of high energy consumption brought by traditional separation technologies in industry today. High-nuclearity metal cluster-based MOFs with different functionalities are promising for this separation, but it is a complicated and difficult task to precisely control their structures. The strategy of pore-space partition (PSP) is a powerful way to construct this type MOFs, which has the characteristic of isostructural relationship, and can be resulted in a similar performance for them. Therefore, it is an interesting work to explore the effect of MOFs property by adjusting the size of PSP dividers. Herein, three tetranuclear Cu(II) cluster-based MOFs (FJU-112/113/114) with dual functionalities has been successfully obtained by PSP strategy with various lengths of divider units. With the highest microporosity and unique functional site, FJU-114 realized a good improvement in the adsorption and separation performance of C2H2/CO2. The gas adsorption and lab-scale C2H2/CO2 breakthrough experiments demonstrated that FJU-114 exhibits the highest adsorption uptake of 77 cm3/g for C2H2, and shows the best separation factor of 4.2 among three MOFs. The GCMC simulation reveals that a stronger adsorption binding site of C2H2 in FJU-114a located in the cage II near the unchanged tetranuclear copper node, combined with its high microporosity to achieve the effect of dual functionalities for the improvement performance of C2H2 adsorption and separation.