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[Cu₂(bdc)₂(bpy)]ₙ/SPES-C mixed matrix membranes for separation of methanol/methyl tert-butyl ether mixtures
Summary:
The authors from Xiamen University developed [Cu₂(bdc)₂(bpy)]ₙ/SPES-C mixed-matrix membranes with nano-MOF fillers, achieving a methanol permeation flux of 0.288 kg m⁻² h⁻¹ and a separation factor up to 2290 for methanol/MTBE pervaporation.
Background:
1. To break the methanol–MTBE azeotrope, earlier PV membranes relied on zeolites or silica fillers; successes were limited by filler/polymer incompatibility and the permeability-selectivity trade-off.
2. The team proposed room-temperature-synthesized [Cu₂(bdc)₂(bpy)]ₙ as a MOF filler and obtained defect-free MMMs that simultaneously enhance both flux and selectivity.
Research Content:
1. Synthesis: [Cu₂(bdc)₂(bpy)]ₙ was precipitated at 25 °C from Cu(OAc)₂, H₂bdc and bpy in MeOH/acetic acid; SPES-C (DS = 0.64) was cast from NMP with 5–30 wt % MOF to give 24 µm films.
2. Characterizations:
1) BET 970 m² g⁻¹, micro-pores 0.7–1.2 nm; preferential MeOH adsorption (155 mg g⁻¹ vs 20 mg g⁻¹ MTBE).
2) SEM/TEM: 35–55 nm cubic MOF crystals uniformly dispersed; AFM RMS roughness 7.8–15 nm.
3) PALS: free-volume cavity radius increases from 0.27 to 0.34 nm with 30 wt % MOF; TGA stable to 200 °C.
3. Application: 15 wt % MeOH/MTBE feed at 40 °C; M-20 membrane delivers flux 0.288 kg m⁻² h⁻¹, separation factor 1870, MeOH permeance 388 gpu—outperforming most literature data.
4. Mechanism: MOF cages provide rapid MeOH diffusion highways while MTBE is sterically retarded; sorption selectivity (8.5) and diffusion selectivity (270) synergistically raise overall selectivity.
Outlook:
The work demonstrates a scalable, low-temperature route to MOF-based MMMs that overcome the traditional permeability-selectivity ceiling, offering a practical platform for green methanol recovery from etherification units.
[Cu₂(bdc)₂(bpy)]ₙ/SPES-C mixed matrix membranes for separation of methanol/methyl tert-butyl ether mixtures
Authors: Guang Lu Han, Ke Zhou, Ao Nan Lai, Qiu Gen Zhang, Ai Mei Zhu, Qing Lin Liu
DOI: 10.1016/j.memsci.2013.11.062
Link: https://www.sciencedirect.com/science/article/pii/S0376738813009459
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