Two Stable Zn-Cluster-Based Metal–Organic Frameworks with Breathing Behavior: Synthesis, Structure, and Adsorption Properties

Two stable Zn-cluster-based MOFs, [Zn₉(btz)₁₂(atdbc)₃(DMF)]·3DMF·12H₂O (compound 1, Hbtz = 1H-benzotriazole, H₂atdbc = 4,4′-(4-amino-1,2,4-triazol-3,5-diyl)­dibenzoic acid, DMF = N,N-dimethylformamide) and [Zn₄(btz)₆(bcpt)]·3DMF (compound 2, H₂bcpt = 3,5-bis­(4′-carboxy-phenyl)-1,2,4-triazole), have been successfully constructed by adopting the mixed ligands approach. Both the compounds exhibit high chemical stability under aqueous solution and common organic solvents. Especially, compounds 1 and 2 can be stable in pH = 2 and pH = 12 solutions. Meanwhile, compound 1 exhibits good ability to selectively separate CO₂ from CH₄. CO₂ over CH₄ selectivity is 5.2 (0.5/0.5) and 5.7 (0.05/0.95) at 298 K under 1 bar, respectively, which may be used for the separation of gases in industrial applications. Moreover, compound 1 displays breathing behavior for small-molecule gases (N₂, CO₂, C₂H₆, and C₃H₈), and compound 2 only exhibits the same phenomenon for CO₂ adsorption because of its ultramicroporous channels.