Design of a MOF based on octa-nuclear zinc clusters realizing both thermal stability and structural flexibility.

An octa-nuclear zinc (Zn 8 ) cluster-based two-fold interpenetrated metal-organic framework (MOF) of [(CH 3 ) 2 NH 2 ] 2 [Zn 8 O 3 (FDC) 6 ]·7DMF (denoted as Zn8-as; H 2 FDC = 9 H -fluorene-2,7-dicarboxylic acid; DMF = N , N -dimethylformamide) was synthesized by the reaction of a hard base of a curved dicarboxylate ligand (H 2 FDC) with the borderline acid of Zn(II) under solvothermal conditions. Zn8-as shows significant crystal volume shrinkage upon heating, yielding a solvate-free framework of [(CH 3 ) 2 NH 2 ] 2 [Zn 8 O 3 (FDC) 6 ] (Zn8-de). Zn8-de displays gated adsorption for C 2 H 2 and type-I adsorption for CO 2 , attributed to the framework flexibility and the different interactions between the gas molecules and the host framework.