Pore-in-Pore Engineering in a Covalent Organic Framework Membrane for Gas Separation

Area of Science:

• Materials Science
• Chemical Engineering
• Nanotechnology

Background:

• Covalent organic framework (COF) membranes show promise for energy-efficient gas separations.
• Precise control over subnanometer pore sizes in COF membranes is crucial but challenging for gas separation applications.

Purpose of the Study:

• To engineer COF membranes with angstrom-precision controlled pore channels for enhanced gas separation.
• To introduce an ultramicropore-in-nanopore strategy using encapsulated α-cyclodextrin (α-CD) within COF channels.

Main Methods:

• In situ encapsulation of α-cyclodextrin (α-CD) during interfacial polymerization of COF.
• Formation of linear assemblies (LA) of α-CD within the 1D nanochannels of the COF membrane.
• Fabrication and characterization of the LA-α-CD-in-TpPa-1 membrane.

Main Results:

• The developed membrane exhibits high H2 permeance (approximately 3000 GPU).
• Achieved enhanced selectivity for H2 over CO2 and CH4 (>30).
• Demonstrated performance exceeding the Robeson upper bounds for H2/CO2 and H2/CH4 separations.

Conclusions:

• The ultramicropore-in-nanopore concept enables fast and selective H2 transport pathways.
• This strategy significantly advances COF membrane performance for H2-selective separations.
• The approach is versatile, applicable to synthesizing various LA-α-CD-in-COF membranes.