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Nanoporous Fluorinated Metal–Organic Framework-Based Membranes for CO₂ Capture
Summary:
The authors from King Abdullah University of Science and Technology (KAUST) developed nanoporous fluorinated SIFSIX-3-M (M = Ni, Cu) MOF membranes grown by liquid-phase epitaxy (LPE), achieving record CO₂-selective separation over H₂ and CH₄ in membrane-based carbon-capture applications.
Background:
1. To address energy-intensive CO₂ capture, previous researchers explored zeolite, polymer and mixed-matrix membranes, achieving moderate selectivity, yet faced issues of defects, low permeability or poor stability.
2. The authors herein proposed LPE fabrication of continuous, defect-free SIFSIX-3-M pure MOF membranes for the first time, demonstrating unprecedented reversed CO₂/H₂ selectivity.
Research Content:
1. Synthesis:
SIFSIX-3-M membranes were synthesized on porous Al₂O₃ substrates via layer-by-layer LPE cycles (30 cycles, 65 °C, methanolic CuSiF₆ or NiSiF₆ followed by pyrazine).
2. Characterizations:
1) XRD confirmed phase purity and preferential (100) orientation exposing 1-D channels (~3.7–3.8 Å).
2) SEM showed dense, crack-free, ~5 µm-thick films of inter-grown microcrystals.
3) Single-gas permeation (CV/VP) and mixed-gas VP-MS tests provided permeability, time-lag and real selectivity data.
3. Application:
Membranes were tested for CO₂/H₂ (30/70) and CO₂/CH₄ (50/50) separation at 2 bar, 308 K; SIFSIX-3-Cu gave α CO₂/H₂ ≈ 27 and CO₂/CH₄ ≈ 15, while SIFSIX-3-Ni reached α CO₂/H₂ ≈ 20 and CO₂/CH₄ ≈ 10.
4. Mechanism:
Solution–diffusion analysis revealed CO₂ permeation governed by high adsorption selectivity (SIS) outweighing diffusion hindrance; preferential channel exposure and fluorinated pore walls provide strong CO₂ affinity, blocking H₂/CH₄ transport in mixtures.
Outlook:
This work pioneers defect-free fluorinated MOF membranes, translating exceptional CO₂ adsorption into membrane separation with record selectivity for pre/post-combustion capture and natural-gas upgrading, and sets a benchmark for future MOF membrane design.
Nanoporous Fluorinated Metal–Organic Framework-Based Membranes for CO₂ Capture
Authors: Valeriya Chernikova, Osama Shekhah, Youssef Belmabkhout, Mohamed Eddaoudi
DOI: 10.1021/acsanm.0c00909
Link: https://pubs.acs.org/doi/10.1021/acsanm.0c00909
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