Building Stable Pillar-Layered Metal–Organic Frameworks: Introduction of Unsaturated Bonds for Enhanced Efficiency in C₂H₂/CO₂ Separation

Abstract

Pillar-layered structures represent a significant category within MOFs; however, the exploration of their chemical stability and systematic functionalization has been largely neglected. Herein, we fabricated a pillarlayered MOF (Zn-L C−C ) with fsc topology, utilizing a tetradentate carboxylic ligand with bipyridine and Zn(II) ions via the pillar-layered approach. Notably, this topological structure displays markedly superior stability compared with typical pillar-layered MOFs with pcu topology. In addition, by introducing unsaturated bonds to modify and increase the length of the pillars, three additional pillar-layered MOFs (Zn-L N=N , Zn-L C=C , and Zn-L C≡C ) were obtained. Compared with those of Zn-L C−C , the adsorption capacities for C 2 H 2 of the other three structures have been improved. Strikingly, the dynamic adsorption uptake of Zn-L N=N for C 2 H 2 is as high as 53.7 cm 3 g −1 , and the dynamic separation ratio of C 2 H 2 /CO 2 is 3.2. These results demonstrate that the introduction of diazo groups in the pillar can enhance the adsorption capacities of pillar-layered MOFs to C 2 H 2 .