Process intensification of synthesis of metal organic framework particles assisted by ultrasound irradiation

Yu Ogura; Keita Taniya; Takafumi Horie; Kuo-Lun Tung; Satoru Nishiyama; Yoshiyuki Komoda; Naoto Ohmura

doi:10.1016/j.ultsonch.2023.106443

Process intensification of synthesis of metal organic framework particles assisted by ultrasound irradiation

Ultrason Sonochem. 2023 Jun:96:106443. doi: 10.1016/j.ultsonch.2023.106443. Epub 2023 May 18.

Authors

Yu Ogura¹, Keita Taniya¹, Takafumi Horie², Kuo-Lun Tung³, Satoru Nishiyama¹, Yoshiyuki Komoda¹, Naoto Ohmura⁴

Affiliations

¹ Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, Japan.
² Department of Chemical Engineering, Graduate School of Engineering, Osaka Metropolitan University, Japan.
³ Department of Chemical Engineering, National Taiwan University, Taiwan.
⁴ Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, Japan. Electronic address: ohmura@kobe-u.ac.jp.

Abstract

This study synthesized UiO-66, a typical Zr-Metal Organic Framework (MOF), by using an ultrasound-assisted synthesis method to reduce the synthesis time. This method was short-time ultrasound irradiation at the initial stage of the reaction. As compared with average particle size of conventional solvothermal method (=192 nm), averaged particle size by the ultrasound-assisted synthesis method showed particle sizes that were smaller on average, ranging from 56 to 155 nm. In order to compare the relative reaction rates of the solvothermal method and the ultrasound-assisted synthesis method, the cloudiness of the reaction solution in the reactor was observed with a video camera, and the luminance was calculated from the images obtained by the video camera. It was found that the ultrasound-assisted synthesis method showed a faster increase in luminance and shorter induction time than the solvothermal method. The slope of the luminance increase during the transient period was also found to become increase with the addition of ultrasound, which also affects the growth of particles. Observation of the aliquoted reaction solution confirmed that particle growth was faster in the ultrasound-assisted synthesis method than in the solvothermal method. Numerical simulations were also performed using MATLAB ver. 5.5 to analyze the unique reaction field generated by ultrasound. Bubble radius and temperature inside a cavitation bubble was obtained using the Keller-Miksis equation, which reproduces the motion of a single bubble. The bubble radius expanded and contracted repeatedly according to the ultrasound sound pressure, and eventually collapsed. The temperature at the time of collapse was extremely high, exceeding 17,000 K. It was confirmed that the high-temperature reaction field generated by ultrasound irradiation promoted nucleation, leading to a reduction in particle size and induction time.

Keywords: Process intensification; UiO-66; Ultrasound-assisted synthesis method; Zr-MOF.