The chemical stability of ZIF-8 in aldehyde under air conditions

Abstract

The chemical stability of zeolitic imidazolate framework-8 (ZIF-8) in water, acid, base and organic solvent has been widely investigated. However, whether it is stable in aldehydes, which are common reactants, has rarely been considered. Herein, the partial or whole dissolution of ZIF-8 with 50 nm and 1000 nm sizes was observed in crotonaldehyde under air conditions. More importantly, the residual ZIF-8 gradually evolved from the original rhombic dodecahedra into a new octahedron morphology and still preserved the ZIF-8 phase structure. A series of experiments revealed that the essence of ZIF-8 degradation in crotonaldehyde is the presence of H⁺, derived from the autoxidation of crotonaldehyde exposing in the air to the corresponding acids. H⁺ could preferentially attack the Zn–N coordination bond located at the {211} edge and {111} vertices with {110} facet shrinkage of the rhombic dodecahedra, leading to the morphological reconstruction of ZIF-8. A further dynamic track showed that the dissolved ratio of ZIF-8 highly depended on the acidic value of crotonaldehyde, temperature and contact time. The dissolution process followed a shrinking core model and was controlled by the diffusion of the H⁺ step.