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Amino-Modified Fe-Terephthalate Metal–Organic Framework as an Efficient Catalyst for the Selective Oxidation of H₂S
Summary：
The authors from the National Engineering Research Center of Chemical Fertilizer Catalyst (Fuzhou University) developed an amino-functionalized Fe-terephthalate metal–organic framework NH₂-MIL-53(Fe), which exhibits high H₂S conversion and ≈100 % sulfur selectivity at 130–160 °C, outperforming commercial Fe₂O₃ and activated carbon in the selective oxidation of H₂S to elemental sulfur.
Background：
1. Traditional Claus technology leaves 3–5 % H₂S unconverted, while existing iron-based catalysts suffer from poor sulfur selectivity and rapid deactivation.
2. The authors propose introducing –NH₂ groups into the MIL-53(Fe) framework to create moderate basic sites and lower activation energy, achieving superior low-temperature performance.
Research Content：
1. Synthesis
NH₂-MIL-53(Fe) and MIL-53(Fe) were synthesized via facile one-pot hydrothermal methods using Fe(NO₃)₃·9H₂O/H₂ATA or FeCl₃·6H₂O/H₂BDC in DMF at 150–170 °C.
2. Characterizations
1) BET: breathing effect causes small, variable surface areas; pore volume not reliably determined.
2) SEM: NH₂-MIL-53(Fe) shows uniform 1.2 × 0.5 µm spindle-like particles vs. larger, irregular MIL-53(Fe).
3) XRD, FT-IR, XPS, TGA, CO₂-TPD confirm crystallinity, thermal stability to 300 °C, Fe³⁺ state, and abundant moderate basic sites from –NH₂.
3. Application
Fixed-bed tests (0.5 % H₂S, 0.25 % O₂, N₂ balance, WHSV = 3000 mL g⁻¹ h⁻¹): NH₂-MIL-53(Fe) reaches 100 % H₂S conversion at 130 °C and maintains >90 % sulfur selectivity up to 160 °C; activation energy drops from 17.15 (MIL-53) to 15.66 kJ mol⁻¹.
Stability: 100 % conversion for 17 h at 160 °C, then gradual decline to 94 %; five-cycle reusability with ≈90 % selectivity retained.
4. Mechanism
–NH₂ groups act as Brønsted bases adsorbing acidic H₂S; O₂ forms O⁻/O₂⁻ active species on Fe³⁺ sites; surface reaction yields S and H₂O while suppressing SO₂/SO₄²⁻ by inhibiting sulfur radicals and Fe–S bond formation.
Outlook：
This work demonstrates the first application of amino-functionalized Fe-MOFs for H₂S selective oxidation, providing a low-temperature, highly selective, and recyclable desulfurization catalyst and a blueprint for MOF-based redox catalyst design.
Amino-Modified Fe-Terephthalate Metal–Organic Framework as an Efficient Catalyst for the Selective Oxidation of H₂S
Authors: Xiao-Xiao Zheng, Li-Juan Shen, Xiao-Ping Chen, Xiao-Hai Zheng, Chak-Tong Au, Li-Long Jiang*
DOI: 10.1021/acs.inorgchem.8b01232
Link: https://pubs.acs.org/doi/10.1021/acs.inorgchem.8b01232
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