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An Amine‐Functionalized Iron(III) Metal–Organic Framework as Efficient Visible‐Light Photocatalyst for Cr(VI) Reduction
Summary:
The authors from Graduate School of Chemical Sciences and Engineering, Hokkaido University; International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), etc. developed amine-functionalized iron(III) metal–organic frameworks (NH₂–MIL-88B(Fe)) with high stability and efficient visible-light photocatalytic activity, achieving excellent performance in the photocatalytic reduction of Cr(VI) in the field of environmental pollution treatment.
Background:
1. Hexavalent chromium (Cr(VI)) is a highly toxic heavy metal pollutant, and reducing it to Cr(III) is an effective treatment method. Traditional photocatalysts like TiO₂ have narrow light response ranges, while sulfide materials suffer from photocorrosion, limiting their applications.
2. The authors proposed using amine-functionalized iron(III)-based MOFs as photocatalysts, which exhibit enhanced visible-light absorption and electron transfer efficiency, achieving efficient reduction of Cr(VI).
Research Content:
1. Synthesis:
The authors synthesized MIL-88B(Fe) and NH₂–MIL-88B(Fe) using a microwave-assisted solvothermal method, with FeCl₃·6H₂O as the metal source and BDC or BDC–NH₂ as organic linkers. Mixed MIL-88B(Fe) with different ratios of BDC and BDC–NH₂ were also prepared.
2. Characterizations:
1) BET and pore size distribution: Not explicitly mentioned, but the materials have porous structures as MOFs.
2) SEM tests show MIL-88B(Fe) is spindle-shaped (5.5 µm in length, 3.2 µm in diameter); NH₂–MIL-88B(Fe) is needle-shaped (1.6 µm in length, 260 nm in diameter).
3) XRD confirmed the MIL-88B structure; UV-vis diffuse reflectance spectra showed enhanced visible-light absorption with amine functionalization; XPS indicated Fe³⁺ in the framework and Cr(III) formation after reaction; PL, ESR, and transient photocurrent tests verified electron transfer.
3. Application:
The materials were used for photocatalytic reduction of Cr(VI) under visible light. NH₂–MIL-88B(Fe) showed the highest activity, reducing Cr(VI) almost completely within 45 min at pH 2, with better performance than P25 under UV-visible light. It had good reusability over four cycles.
4. Mechanism:
A dual excitation pathway was proposed: visible light excites both amine-functionalized organic linkers and Fe₃-μ₃-oxo clusters. Electrons from excited linkers transfer to Fe₃-μ₃-oxo clusters, and electrons from both sources reduce Cr(VI) to Cr(III), enhancing photocatalytic efficiency.
Outlook:
This research demonstrates that amine functionalization can effectively improve the visible-light photocatalytic activity of iron(III)-based MOFs, providing a new strategy for designing efficient and stable photocatalysts for environmental remediation.
An Amine‐Functionalized Iron(III) Metal–Organic Framework as Efficient Visible‐Light Photocatalyst for Cr(VI) Reduction
Authors: Li Shi, Tao Wang, Huabin Zhang, Kun Chang, Xianguang Meng, Huimin Liu, Jinhua Ye
DOI: 10.1002/advs.201500006
Link: https://onlinelibrary.wiley.com/doi/10.1002/advs.201500006
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