Flowability improvement of soft metal-organic framework particles by wet granulation

摘要

Owing to their step-wise adsorption behavior induced by structural transition, soft metal-organic frameworks (soft MOFs) are used in a wide range of applications. However, they suffer from poor handling performance because of their submicron size. Hence, it is imperative to improve their flowability in order to render them suitable for industrial applications. In this study, we used wet granulation to improve the flowability of zeolitic imidazolate framework-8 (ZIF-8), which consists of zinc ions and 2-methylimidazolate linkers and exhibits intraframework flexibility. A high-shear mixing granulator was employed to carry out the wet granulation of the ZIF-8 particles using water and hydroxypropyl cellulose as the binder. The binder and liquid binder concentrations controlled the granule size from 100 to 400 Ism, regardless of the primary diameters of the ZIF-8 particles. In addition, the larger granules showed significant improvement in the flowability. The adsorption capacity of the ZIF-8 granules decreased slightly with an increase in the binder concentration. On the other hand, the gate adsorption behavior of ZIF-8 remained almost unchanged even after the granulation process.