Construction of new multi-cage-based MOFs using flexible triangular ligands for efficient gas adsorption and separation

Designing efficient absorbents for multi-gas adsorption and separation is of critical significance for gas purification in chemical engineering. Multi-cage structure enables sufficient interactions with multi-gas through the restriction effects, which is promising to achieve high multi-gas separation performance. In this work, two isomorphic metal-organic frameworks (MOFs) (SNNU-275, M ​= ​Cu, and SNNU-276, M ​= ​Ni) with three types of cages (octahedral M 6 L 4 , cuboctahedral M 12 L 8 , and M 12 L 24 ), which are (3,4)-linked three-dimensional microporous structures formed by stacking M 6 (TPA) 4 octahedral coordination molecular cages are synthesized by using tri(4-pyridyl) amine (TPA) ligands and Cu/Ni metals. TPA is selected as the central ligand due to the small size and flexible characteristics. The synthesized SNNU-275 exhibits a good combination of high C 2 H 2 /CO 2 adsorption selectivity (28), while high C 2 H 2 uptake capacity (68 ​cm 3  ​g −1 ) is achieved for SNNU-276 with high stability. In addition, SNNU-275 and SNNU-276 exhibited superior uptake capacity for benzene and water vapor. Overall, this work not only provides new triangular tripyridine-based MOFs with multiple cages for efficient gas purification, but also demonstrated that the multicage engineering is a promising strategy for the multicomponent gas separation.