Identifying synthetic variables influencing the reproducible microfluidic synthesis of ZIF nano- and micro-particles

Abstract

The reproducible synthesis of nano- and -micro particles is a critical step in multiple synthetic and industrial processes. Microfluidic synthesis offers numerous advantages for development of precise, reliable, and industrially useful synthesis protocols. However, the influence of different synthetic variables on reproducibility in microfluidic synthesis is underexplored. In this work, we systematically study the influence of key synthetic parameters on the microfluidic synthesis of four Zeolitic Imidazolate Frameworks (ZIFs): ZIF-7, ZIF-8, ZIF-9, and ZIF-67. Utilizing a coiled tube microfluidic setup, we explore the influence of key synthetic parameters such as reagent concentration, stoichiometry, aging time, and nine modulators (pH-altering agents, surfactants, and polar polymers). Most importantly, we evaluate the impact of these variables in combination with the role of mixing, using the Dean flow model. Lastly, we focus on the reproducibility problems that a coiled reactor presents at specific flowrates and how these problems can be recognized and avoided. Overall, the insights collected from this work inform the design of synthetic protocols and enhance material reproducibility and control in microfluidic nano- and micro-particle synthesis.