Angstrom-Scale Defect-Free Crystalline Membrane for Sieving Small Organic Molecules.

Area of Science:

• Materials Science
• Chemical Engineering
• Nanotechnology

Background:

• Metal-organic frameworks (MOFs) with angstrom-sized apertures show promise for molecular separation.
• Separating small molecules with similar sizes is difficult due to angstrom-scale defects in MOF membranes.

Purpose of the Study:

• To develop a novel strategy for constructing MOF membranes with intrinsic angstrom-sized lattice apertures.
• To achieve efficient separation of organic azeotropic mixtures using defect-free MOF membranes.

Main Methods:

• A stepwise assembling strategy involving redesigning the metal source and introducing extra ligands.
• Synthesizing MOF membranes to minimize cluster-missing and linker-missing defects.
• Utilizing ultralow-dose transmission electron microscopy for defect observation.

Main Results:

• The developed MOF membrane exhibits angstrom-scale defect-free lattice apertures.
• Successfully separated challenging methanol-containing ester or ether azeotropic mixtures (<1 Å molecular size difference).
• Achieved an outstanding flux of ≈3700 g·m⁻²·h⁻¹ and separation factors of ≈247-524.

Conclusions:

• The stepwise assembling strategy enables precise construction of angstrom-confined spaces.
• The defect-free MOF membrane significantly outperforms state-of-the-art membranes for challenging separations.
• This approach offers a feasible strategy for diverse applications including separation, catalysis, and storage.