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

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 pillar-layered MOF (Zn-LC–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-LN=N, Zn-LC=C, and Zn-LC≡C) were obtained. Compared with those of Zn-LC–C, the adsorption capacities for C2H2 of the other three structures have been improved. Strikingly, the dynamic adsorption uptake of Zn-LN=N for C2H2 is as high as 53.7 cm3 g–1, and the dynamic separation ratio of C2H2/CO2 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 C2H2.