The pressure-induced rotation of the imidazolate in Zeolitic Imidazolate Frameworks (ZIFs) is accompanied by an increase of their pore openings, affecting ZIFs performance in separation processes. This phenomenon is known as the gate opening or the swing effect. We show by using periodic Kohn-Sham density functional calculations that metal substitution (Mg, Fe, and Zn) is a very effective way to tune the flexibility of ZIF-8 materials (see Figure 1). For both the magnesium- and the iron-based system the gate opening phenomenon requires half and a fourth of the energy than for the zinc material, respectively. The metal determines also the most stable phase of the material. Because of the importance of ZIF-8 among porous materials and because the gate opening is its most studied property, our results strongly call for future high-pressure diffraction studies aimed at the experimental verification of the present findings.

Swing effect dependence on metal substitution in ZIF-8 materials

ACS Fall 2021

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