Structure Screening of Oscillating Feedback Microreactors for the High-Throughput Synthesis of Zeolitic Imidazolate Framework-67 Nanoparticles with Controlled Size and Morphology

The relationship between the flow pattern evolution and performance of oscillating feedback microreactors (OFMs) for the synthesis of ZIF-67 nanoparticles was investigated by a photomicrography technique. Accordingly, an oscillating feedback microreactor (OFM) with an optimized structure was identified for high-throughput ZIF-67 production. By varying the experimental conditions (i.e., flow rate, aging time, precursor concentration [Co2+], solvent, and cobalt source), the average size of ZIF-67 products can be adjusted (from 16 to 294 nm) with narrow particle size distribution (geometric standard deviation: 1.08-1.14) as well as with controllable morphology (sphere or rhombic dodecahedron). The maximum total flow rate can reach 160 mL/min, indicating that a high-throughput synthesis of ZIF-67 is achieved. The screening method can be extended to optimize other microreactors, and the resulting OFMs can be applied to produce other kinds of nanoparticles.