Controlled synthesis of ZIFs by microemulsion method at high-throughput in a chaotic microreactor

The average size and particle size distribution (PSD) of zeolitic imidazolate frameworks (ZIFs) (such as ZIF-8, ZIF-67) are closely related to their physical and chemical properties. However, it is difficult to prepare small ZIFs with narrow PSD in traditional batch reactors owing to poor mixing efficiency. Here, a four-stage oscillating feedback microreactor (FOFM) was developed to prepare ZIFs by microemulsion method. CFD simulations and visualization experiments were conducted to investigate liquid-liquid two-phase flow patterns involved, demonstrating that chaotic advection can be effectively produced, thus dispersed phase is broken up into small droplets and homogeneous microemulsions are obtained. The proposed microemulsion method based on FOFM enables preparation of ZIF-8 with small average size (38.2 nm) and narrow PSD (sigma g = 1.24) without surfactant at a flow rate of 90 mL/min.