Issue 42, 2022

Preparation of ZIF-8-coated silica hard-shell microcapsule by semi-batch operation

Abstract

This paper reports the selective fabrication of a zeolitic imidazolate framework-8 (ZIF-8) cover layer over the outer surface of silica hard-shell microcapsules (HSMC) to improve the microencapsulation technique of phase change materials for heat storage materials. ZIF-8 was formed not only over the HSMC but also in the synthesis solution side when using a conventional batch operation owing to the rapid formation rate of ZIF-8 in the aqueous solution at 293 K. In this study, a semi-batch operation, which can control the concentration of the components in the synthesis solution by gradually dropping the components, was employed to decrease the formation rate of ZIF-8. X-ray diffraction results suggested that dropping ingredients strongly affected the obtained products; the addition of the Zn2+ aqueous solution into a 2-methylimidazole (Hmim) aqueous solution was suitable for the formation of ZIF-8, whereas the addition of an aqueous solution of Hmim into the Zn2+ aqueous solution formed Zn hydroxides as unfavorable by-products. Field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy results confirmed that the semi-batch operation with the addition of Zn2+ into the Hmim aqueous solution selectively formed a ZIF-8 cover layer over the HSMC. We conclude that the semi-batch operation is an effective procedure for suppressing the unfavorable homogeneous nucleation on the solution side and making heterogeneous nucleation dominant without any additives to fabricate the ZIF-8 cover layer.

Graphical abstract: Preparation of ZIF-8-coated silica hard-shell microcapsule by semi-batch operation

Supplementary files

Article information

Article type
Paper
Submitted
07 Apr 2022
Accepted
10 Sep 2022
First published
15 Sep 2022

CrystEngComm, 2022,24, 7378-7386

Author version available

Preparation of ZIF-8-coated silica hard-shell microcapsule by semi-batch operation

S. Kawada, T. Otsubo, T. Horie, Y. Komoda, N. Ohmura, H. Asano, R. Hidema, H. Suzuki, K. Taniya, Y. Ichihashi and S. Nishiyama, CrystEngComm, 2022, 24, 7378 DOI: 10.1039/D2CE00488G

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements