Specific anion effects on the stability of zeolitic imidazolate framework-8 in aqueous solution

In this study, the stability of zeolitic imidazolate framework-8 (ZIF-8) was investigated in 7 common anions aqueous solutions. Experimental results showed that Cl⁻, SO₄ ²⁻, NO₃ ⁻, PO₄ ³⁻, and CO₃ ²⁻ have insignificant change in the crystallinity and permanent porosity of ZIF-8 by SEM, XRD, nitrogen sorption and dissolution of Zn and 2-methylimidazole (Hmim) characterizations. Nevertheless, ZIF-8 crystalline phase and its porous character are transformed by the presence of HCO₃ ⁻ and HPO₄ ²⁻.The dissolution of Zn and Hmim underwent a process of a giant ascent at the first stage and a following drop until a steady state in the two mediums. On the other hand, the morphology of ZIF-8 and the XRD peaks changes apparently in the both solutions. However, ZIF-8 possesses a higher stability when Hmim is introduced in the solution due to the inhibiting re-dissolution of ZIF-8 in the two solutions.