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

Chechia Hu, Yu Chi Huang, Ai Lun Chang, Mikihiro Nomura

Research output: Contribution to journalArticle

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, kSSA), 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.

Original languageEnglish
Pages (from-to)372-381
Number of pages10
JournalJournal of Colloid and Interface Science
Volume553
DOIs
Publication statusPublished - 2019 Oct 1

Fingerprint

Photocatalysts
Amines
ethylenediamine
Specific surface area
Poisons
Chemical stability
Light absorption
Nuclear magnetic resonance spectroscopy
Fourier transform infrared spectroscopy
Carrier concentration
chromium hexavalent ion
Zinc
Rate constants
Chromium
Catalyst activity
X ray photoelectron spectroscopy
Porosity
Metals
Irradiation

Keywords

  • Amine functionalization
  • Cr reduction
  • Photocatalysis
  • ZIF-8

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Surfaces, Coatings and Films
  • Colloid and Surface Chemistry

Cite this

Amine functionalized ZIF-8 as a visible-light-driven photocatalyst for Cr(VI) reduction. / Hu, Chechia; Huang, Yu Chi; Chang, Ai Lun; Nomura, Mikihiro.

In: Journal of Colloid and Interface Science, Vol. 553, 01.10.2019, p. 372-381.

Research output: Contribution to journalArticle

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AB - 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, kSSA), 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.

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