Synthesis and adsorption properties of ZIF-8 nanoparticles using a micromixer

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2013-07, Vol.227, p.145-150
• Main Authors: Yamamoto, Daigo, Maki, Taisuke, Watanabe, Satoshi, Tanaka, Hideki, Miyahara, Minoru T., Mae, Kazuhiro
• Format: Article
• Language: English
• Subjects: Adsorption; chemical engineering; Flow rate; ions; Laminar flow; Metal organic frameworks; Micromixer; mixing; Nanocrystals; Nanoparticles; Porous coordination polymers; Raw materials; Resultants; temperature; Turbulence; turbulent flow
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2012.08.065

[Display omitted] ► Size-controlled ZIF-8 nanoparticles are prepared using a T-type micromixer. ► Size and shape of the ZIF-8 nanoparticles depends on mixing process of raw materials. ► Lowering temperatures increases the number of nuclei during the nucleation process. ► Ratios of concentrations of raw materials affect the particle growth process. ► The ZIF-8 nanoparticles have high adsorption properties compared to the bulk. We synthesized size-controlled zeolitic imidazolate framework (ZIF-8) nanoparticles using a T-type micromixer. The nanocrystallization of ZIF-8 proceeds by a rapid coordination reaction of Zn2+ ions and 2-methylimidazole (2-MeIM) in a highly concentrated solution. Therefore, a rapid mixing of the raw materials is required to control the size and morphology of ZIF-8 nanoparticles. First, we prepared ZIF-8 nanoparticles at various flow rates of raw materials to investigate the mixing performance of a T-type micromixer. The size of the ZIF-8 nanoparticles decreased with an increase in flow rates at Reynolds number (Re)2000 (transition state between laminar flow and turbulent flow), demonstrating the high mixing performance. Further, we systematically examined the effects of temperatures and [2-MeIM]/[Zn2+] ratios on the resultant ZIF-8 nanoparticles to elucidate the formation mechanism and to optimize the conditions for the synthesis of smaller ZIF-8 nanoparticles. Through a detailed analysis, we concluded that the requisite conditions for the preparation of smaller ZIF-8 nanoparticles are lower temperatures and higher [2-MeIM]/[Zn2+] ratios, which affect the nucleation process and the particle growth process, respectively. Finally, we examined the adsorption properties of the resultant smaller ZIF-8 nanoparticles. We found that the amount of adsorbed N2 gas for the ZIF-8 nanoparticles synthesized by our method is higher than the amount for a conventional ZIF-8 sample, and the adsorption rate is faster because of the nanocrystallization.