Rational Pore Design of a Cage-like Metal-Organic Framework for Efficient C 2 H 2 /CO 2 Separation.

Considering the importance of C 2 H 2 in industry, it is of great significance to develop porous materials for efficient C 2 H 2 /CO 2 separation. Besides the high selectivity, the C 2 H 2 adsorption capacity is another vital factor in C 2 H 2 /CO 2 separation. However, the "trade-off" between these two factors is still perplexing. Rational pore design of metal-organic frameworks (MOFs) has been proven to be an effective way to solve the above problem. In this work, we have appropriately combined three kinds of strategies in the design of the MOF ( FJI-H33 ), i.e., the introduction of open metal sites, construction of cage-like cavities, and adjustment of moderate pore size. As anticipated, FJI-H33 exhibits both outstanding C 2 H 2 adsorption capacity and high C 2 H 2 /CO 2 selectivity. At 298 K and 100 kPa, the C 2 H 2 storage capacity of FJI-H33 is 154 cm 3 /g, while the CO 2 uptake is only 80 cm 3 /g. The ideal adsorbed solution theory (IAST) selectivity of C 2 H 2 /CO 2 (50:50) is calculated as high as 15.5 at 298 K. More importantly, the excellent practical separation performance was verified by breakthrough experiments. In addition, the calculation of adsorption sites and relevant energy by density functional theory (DFT) provides a good explanation for the excellent separation performance and pore design strategy.