The reaction of Zn(OAc)2·2H2O, NH4F, and 2,6-dimethylbenzo1,2-d:4,5-d′diimidazole (H2bdmim) in isopropanol/ethylene glycol yields a new metal azolate framework, Zn2F(OH)(bdmim)(H2O)·Guest (1·G). Single-crystal X-ray diffraction reveals that 1·G comprises irregular decahedral Zn16F8(bdmim)88+ building blocks interconnected via coplanar Zn4F2(Rim)24+ four-membered rings, forming a three-dimensional (3D) framework with diamond (dia) topology featuring cross-linked 1D channels running along the a- and b-axes. Upon activation, 1·G underwent significant framework contraction via single-crystal-to-single-crystal transformation to afford Zn2F(OH)(bdmim) (1a). Interestingly, removal of the aqua ligands prompts the transformation of the monodentate hydroxy ligands into bridging ones to occupy the vacant coordination sites. This structural reconstruction drives elongation of Zn16F8(bdmim)88+ building blocks and simultaneously shortens their interconnection distances, thereby compressing the 1D channels. Moreover, the structure exhibits exceptional thermal stability (up to 600 °C) and robust acid–base stability (pH = 2–13). Additionally, 1a demonstrates high toluene/methylcyclohexane selectivity of 52, which is primarily attributed to their kinetic differences arising from the compressed pore channels.
Feng et al. (Tue,) studied this question.