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Water Stable Zr–Benzenedicarboxylate Metal–Organic Frameworks as Photocatalysts for Hydrogen Generation
Summary:
The authors from Instituto de Tecnología Química (CSIC-UPV), Spain, developed water-stable Zr-based MOFs (UiO-66 and UiO-66(NH₂)) with semiconductor-like behavior, achieving photocatalytic hydrogen generation under UV-visible light in water/methanol mixtures.
Background:
1. To address the lack of photocatalytic activity in traditional porous materials like zeolites, previous researchers explored MOFs as semiconductors. While some success was achieved in photocatalysis, issues such as poor water stability and low visible-light response remained.
2. This work proposed an innovative strategy: modifying UiO-66 with amino groups to enhance light absorption and utilizing its exceptional water stability for photocatalytic H₂ production.
Research Content:
1. Synthesis:
UiO-66 and UiO-66(NH₂) were solvothermally synthesized using ZrCl₄ and terephthalic acid or 2-aminoterephthalic acid in DMF at 120°C.
2. Characterizations:
- XRD: Confirmed isoreticular structures with high crystallinity.
- UV-Vis: UiO-66(NH₂) showed enhanced absorption (300–440 nm) due to the amino group.
- Laser flash photolysis: Revealed long-lived charge-separated states (>300 μs), supporting semiconductor behavior.
- BET/ICP: High surface area and Zr content confirmed; detailed porosity not fully reported.
3. Application:
Photocatalytic H₂ evolution was tested in water/methanol (3:1) under UV light (λ > 300 nm). UiO-66(NH₂) achieved a 3.5% apparent quantum yield at 370 nm, outperforming UiO-66 (<0.1%) and approaching TiO₂ P25 (4.5 mL H₂ vs. 2.8 mL).
4. Mechanism:
Photoexcitation generates charge separation (e⁻/h⁺). Methanol acts as a sacrificial donor, while Pt nanoparticles enhance H₂ evolution. The amino group induces a red-shift in absorption without altering the photochemistry, improving visible-light utilization.
Outlook:
This study demonstrates the potential of MOFs as stable, tunable photocatalysts for solar fuel generation. Rational linker modification and co-catalyst integration offer promising routes to enhance efficiency and broaden light absorption.
Water Stable Zr–Benzenedicarboxylate Metal–Organic Frameworks as Photocatalysts for Hydrogen Generation
Authors: Cláudia Gomes Silva, Ignacio Luz, Francesc X. Llabrés i Xamena, Avelino Corma, Hermenegildo García
DOI: 10.1002/chem.200903526
Link: https://onlinelibrary.wiley.com/doi/10.1002/chem.200903526
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