Bioinspired Gradient Covalent Organic Framework Membranes for Ultrafast and Asymmetric Solvent Transport.

Area of Science:

• Materials Science
• Membrane Technology
• Nanotechnology

Background:

• Gradients are crucial in membrane technologies for applications like separation and energy conversion.
• Creating functional gradient membranes with controlled porosity and scale remains a significant challenge.

Purpose of the Study:

• To develop a general approach for constructing gradient covalent organic framework membranes (GCOMx).
• To investigate the unique transport properties and potential applications of these GCOMx.

Main Methods:

• Utilized poly(ionic liquid)s (PILs) as templates to create GCOMx with graded distribution of covalent organic framework (COF) crystals.
• Employed hydromechanical theoretical calculations and systematic experiments to verify solvent transport and filtration performance.

Main Results:

• GCOMx demonstrated unprecedented asymmetric solvent transport, with "large-to-small" pore flow exhibiting 10-18 times higher flux.
• Achieved superior permeance for nonpolar (hexane ≈260.45 LMH bar⁻¹) and polar (methanol ≈175.93 LMH bar⁻¹) solvents.
• Exhibited a narrow molecular weight cut-off (MWCO) of 472 g mol⁻¹ and molecular weight retention onset (MWRO) below 182 g mol⁻¹.

Conclusions:

• The developed GCOMx offers a scalable method for creating functional gradient membranes.
• GCOMx show great potential for bionic applications, particularly in simulated kidney dialysis, due to their selective transport properties.