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News > Occurrence of Uncommon Infinite Chains Consisting of Edge-Sharing Octahedra in a Porous Metal Organic Framework-Type Aluminum Pyromellitate Al₄(OH)₈[C₁₀O₈H₂] (MIL-120): Synthesis, Structure, and Gas Sorption Properties
Occurrence of Uncommon Infinite Chains Consisting of Edge-Sharing Octahedra in a Porous Metal Organic Framework-Type Aluminum Pyromellitate Al₄(OH)₈[C₁₀O₈H₂] (MIL-120): Synthesis, Structure, and Gas Sorption Properties
Summary:
The authors from Institut Lavoisier de Versailles, ESRF, ICMPE-CMTR, and Laboratoire Chimie Provence developed a porous metal-organic framework (MOF)-type aluminum pyromellitate Al₄(OH)₈[C₁₀O₈H₂]·4.8-5H₂O (MIL-120) with uncommon infinite chains of edge-sharing octahedra, achieving favorable gas sorption properties in gas storage applications.
Background:
1. To address the demand for porous hybrid materials with well-defined pore systems for molecular storage, separation, etc., previous researchers studied MOFs with various cations and carboxylate linkers. Aluminum-based MOFs were promising but typically had trans-connected corner-sharing octahedra, lacking edge-sharing octahedra chains.
2. The authors proposed hydrothermal synthesis of MIL-120, which features a new open framework with edge-sharing octahedra chains, and investigated its structure and gas sorption properties.
Research Content:
1. Synthesis:
The authors synthesized MIL-120 via hydrothermal method. A mixture of Al(NO₃)₃·9H₂O, pyromellitic acid (H₄btec), 4M NaOH, and deionized water was treated in a 125 mL Parr autoclave at 210°C for 24 h, followed by filtration, washing, and drying.
2. Characterizations:
1) BET surface area was 308(4) m²g⁻¹ (Langmuir: 432(1) m²g⁻¹) with a micropore volume of 0.11 cm³g⁻¹; channels along the c axis had a size of 5.4×4.7 Å.
2) SEM showed MIL-120 consists of 1-10 μm prismatic platelike crystallites.
3) Other tests: XRD confirmed monoclinic system (space group C2/m); ²⁷Al NMR revealed two Al sites (C_Q=8.07 and 4.77 MHz); TG indicated thermal stability up to 340°C.
3. Application:
The material was tested for gas sorption. At 77 K and 3 MPa, H₂ adsorption was 1.3 wt%; at 303 K and 1 MPa, CH₄ and CO₂ adsorptions were 1.8 mmol g⁻¹ and 4.8 mmol g⁻¹, respectively, with good reversibility.
4. Mechanism:
MIL-120 has infinite zigzag chains of AlO₂(OH)₄ octahedra (edge-sharing via μ₂-hydroxo groups) along [102] with cis-trans connection. Pyromellitate linkers connect chains, forming 3D networks with channels. Gas sorption is attributed to microporosity and confinement effects, with adsorption enthalpies reflecting strong interactions.
Outlook:
This research reports MIL-120 with a novel edge-sharing octahedra chain structure, expanding MOF diversity. Its gas sorption properties support potential in gas storage, guiding porous material design.
Occurrence of Uncommon Infinite Chains Consisting of Edge-Sharing Octahedra in a Porous Metal Organic Framework-Type Aluminum Pyromellitate Al₄(OH)₈[C₁₀O₈H₂] (MIL-120): Synthesis, Structure, and Gas Sorption Properties
Authors: Christophe Volkringer, Thierry Loiseau, Mohamed Haouas, Francis Taulelle, Dmitry Popov, Manfred Burghammer, Christian Riekel, Claudia Zlotea, Fermin Cuevas, Michel Latroche, Delphine Phanon, Christina Knöfel, Philip L Llewellyn, Gerard Ferey
DOI: 10.1021/cm9023106
Link: https://pubs.acs.org/doi/10.1021/cm9023106
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