Scalable metal-organic framework membranes through nonclassical crystallization for molecular separation.

Area of Science:

• Materials Science
• Chemical Engineering
• Nanotechnology

Background:

• Metal-organic framework (MOF) membranes offer precise pore size control for selective molecular separations.
• High surface energy of MOF nanodispersions hinders membrane assembly, causing nonselective grain boundaries and poor processability.
• Current methods face challenges in achieving uniform and defect-free MOF membrane structures for industrial use.

Purpose of the Study:

• To develop a novel strategy for fabricating highly precise and structurally uniform MOF membranes.
• To overcome the limitations of high surface energy in MOF nanodispersions for improved membrane assembly.
• To enhance the performance and scalability of MOF membranes for industrial molecular separations.

Main Methods:

• A metastable phase crystallization (MPC) strategy utilizing nonclassical crystallization pathways.
• Integration of sol-gel coating, vapor-phase reactions, and ligand insertion for membrane fabrication.
• Tuning of MOF membrane pore sizes through ligand incorporation.

Main Results:

• Fabrication of MOF membranes with high precision and structural uniformity via MPC.
• Al-MOF membranes exhibited excellent solvent permeance and solute retention.
• Enhanced stability under elevated pressures and long-term operation was demonstrated.
• Tailoring pore sizes through ligand incorporation further improved molecular separation performance.
• A scalable 10-tube tubular MOF membrane module with an effective area of 230 cm² was successfully demonstrated.

Conclusions:

• The MPC strategy offers a viable pathway for defect-free MOF membrane fabrication.
• MPC-based MOF membranes show significant potential for industrial molecular separation processes.
• The developed method allows for tunable pore sizes, leading to improved separation efficiency and scalability.