Pillared Carbon Membranes Derived from Cardo Polymers.

Area of Science:

• Materials Science
• Chemical Engineering
• Polymer Science

Background:

• High free volume polyimides like BTDA-BAF offer potential for gas separation membranes.
• Polyimide-derived carbon molecular sieve membranes (CMSMs) often suffer from pore collapse and aging, limiting their performance.
• Achieving high permeability and selectivity simultaneously remains a challenge in membrane technology.

Purpose of the Study:

• To develop robust carbon molecular sieve membranes (CMSMs) with improved gas separation performance and stability.
• To investigate the effect of incorporating metal-organic polyhedra (MOP-18) on the structure and properties of CMSMs.
• To evaluate the CO2/CH4 separation capabilities and aging resistance of the developed membranes.

Main Methods:

• Synthesis of BTDA-BAF polyimide via polycondensation.
• Preparation of CMSMs by carbonizing BTDA-BAF and MOP-18/BTDA-BAF composites at 550 °C.
• Characterization of membrane structure, including pore collapse and graphitic sheet integrity.
• Gas permeation testing for CO2 and CH4 to determine permeability and selectivity.
• Evaluation of membrane aging over time.

Main Results:

• MOP-18 incorporation and subsequent copper nanoparticle formation prevented pore collapse and membrane aging.
• Pillared CMSMs achieved high CO2 permeability (12,729 Barrer) and CH4 permeability (659 Barrer) with a CO2/CH4 selectivity of 19.3.
• The permselectivity of MOP-18/BTDA-BAF CMSMs reached the 2019 Robeson upper bound.
• Pure BTDA-BAF CMSMs showed lower performance (5337 Barrer CO2, 573 Barrer CH4, 9.3 selectivity) and aged significantly faster.

Conclusions:

• Metal-organic polyhedra-pillared carbon molecular sieve membranes offer superior CO2/CH4 separation performance and enhanced stability.
• The use of MOP-18 effectively mitigates pore collapse and aging in CMSMs, leading to sustained high permselectivity.
• These advanced CMSMs represent a promising direction for efficient natural gas purification and carbon capture technologies.