Dual-function biomimetic carrier based facilitated transport mixed matrix membranes with high stability for efficient CO₂/N₂ separation

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Summary:
Authors from Zhengzhou University & Henan University developed CFA-1/Pebax mixed-matrix membranes that exhibit 869 Barrer CO₂ permeability and 88.6 CO₂/N₂ selectivity (1 bar, 30 °C), outperforming 2008 upper-bound for CO₂/N₂ separation.

Background:
1. To mitigate CO₂ emissions, facilitated-transport polymer membranes have been explored, yet protein carriers (carbonic anhydrase) suffer from high cost, poor thermal/chemical stability and non-porosity.
2. The team proposed a dual-function biomimetic MOF (CFA-1) as a stable, porous, CA-mimic carrier and fabricated Pebax mixed-matrix membranes with record performance.

Research Content:
1. Synthesis: CFA-1 was solvothermally synthesized (Zn acetate + H₂-bibta ligand, 90→120 °C), activated in NaHCO₃, and dispersed in Pebax-1657/ethanol-water to cast 50–60 μm membranes (1–5 wt % filler).
2. Characterizations:
   – BET: CFA-1 microporous, 1056 m² g⁻¹, 0.8 nm pores.
   – SEM: triangular CFA-1 crystals (~μm) uniformly dispersed in Pebax at 3 %; EDS confirms homogeneous distribution.
   – XRD, FTIR, DSC, TGA: crystallinity & CA-like Zn–OH sites retained; membranes thermally stable to 350 °C; Tg rises from –52.9 to –48.0 °C.
3. Application:
   – Pure gas: 869 Barrer CO₂, α(CO₂/N₂)=88.6 (3 % CFA-1) vs 94 Barrer & 31 for neat Pebax.
   – Mixed-gas (10 % CO₂/90 % N₂, dry): 821 Barrer, α=79; humidified: 1409 Barrer, α=83—both exceed 2008 Robeson upper bound.
   – 180 h continuous test: no performance loss; pH 5–11 & 80 °C treatment: stable, whereas Pebax/CA membranes fail.
4. Mechanism: CFA-1 provides (i) 0.8 nm channels enhancing CO₂ diffusion (D ↑ 3.6×) and (ii) Zn–OH sites catalyzing CO₂ hydration (facilitated transport), raising CO₂ solubility (S ↑ 2.6×); cooperative effect breaks trade-off.

Outlook:
The work delivers the first porous CA-mimic MOF-based FT-MMM, combining high permeability, selectivity and robust stability, offering a scalable route for efficient carbon capture membranes.

Dual-function biomimetic carrier based facilitated transport mixed matrix membranes with high stability for efficient CO₂/N₂ separation
Authors: Weigang Zheng, Zhihong Tian, Zhen Wang, Donglai Peng, Yongsheng Zhang, Jing Wang, Yatao Zhang
DOI: 10.1016/j.seppur.2021.120371
Link: https://doi.org/10.1016/j.seppur.2021.120371

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