Amine functionalized ZIF-8 as a visible-light-driven photocatalyst for Cr(VI) reduction

Chechia Hu; Yu-Chi Huang; Ai-Lun Chang; Mikihiro Nomura

doi:10.1016/j.jcis.2019.06.040

Amine functionalized ZIF-8 as a visible-light-driven photocatalyst for Cr^(VI) reduction

J Colloid Interface Sci. 2019 Oct 1:553:372-381. doi: 10.1016/j.jcis.2019.06.040. Epub 2019 Jun 13.

Authors

Chechia Hu¹, Yu-Chi Huang², Ai-Lun Chang², Mikihiro Nomura³

Affiliations

¹ Department of Chemical Engineering, Chung Yuan Christian University, Chungli Dist., Taoyuan City 32023, Taiwan; R&D Center for Membrane Technology and Research Center for Circular Economy, Chung Yuan Christian University, Chungli Dist., Taoyuan City 32023, Taiwan. Electronic address: chechiahu@cycu.edu.tw.
² Department of Chemical Engineering, Chung Yuan Christian University, Chungli Dist., Taoyuan City 32023, Taiwan.
³ Department of Applied Chemistry, Shibaura Institute of Technology, Koto-ku, Tokyo, Japan. Electronic address: Lscathy@shibaura-it.ac.jp.

PMID: 31228752
DOI: 10.1016/j.jcis.2019.06.040

Abstract

Hexavalent chromium (Cr^(VI)) is one of the most toxic and carcinogenic species known to living beings, the environment, and our eco-system. Thus, it is urgent to develop a facile and effective approach for Cr^(VI) removal. Zinc-based zeolitic imidazolate frameworks (ZIF-8), a typical metal organic framework, have high porosity, large specific surface area, high chemical stability, and abundant surface grafting sites. These sites can be easily modified with ethylenediamine (EDA) using a solvothermal process to generate a material that can serve as a potential candidate for photocatalytic Cr^(VI) reduction under visible light irradiation. Various EDA contents and synthetic conditions were adopted in an attempt to investigate the correlation between ZIF-8 amine-functionalization and photocatalytic Cr^(VI) reduction. The amine functionalization and the grafting sites on ZIF-8 were determined to be located at the -CH₃ site of the 2-methylimidazole chains via X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance spectroscopy (NMR). Under optimum conditions, amine-functionalized ZIF-8 exhibited a normalized rate constant (k/specific surface area, k_SSA), which was 9.8 times higher than that of unmodified ZIF-8 one for photocatalytic Cr^(VI) reduction. The increased catalytic activity and range of visible light absorption of amine-functionalized ZIF-8 can be attributed to the increase in electron density due to the lone pairs of the surface grafted amines. In summary, amine-functionalized ZIF-8 could serve as a promising visible-light-active photocatalyst for environmental remediation.

Keywords: Amine functionalization; Cr((VI)) reduction; Photocatalysis; ZIF-8.