Efficient C₂H₂/CO₂ Separation in Ultramicroporous Metal-Organic Frameworks with Record C₂H₂ Storage Density

Area of Science:

• Materials Science
• Chemical Engineering
• Separation Science

Background:

• Physical separation of acetylene (C2H2) from carbon dioxide (CO2) is crucial but challenging due to similar physical properties.
• Existing methods often focus on open metal sites, with less exploration of reticular manipulation of organic components in metal-organic frameworks (MOFs).

Purpose of the Study:

• To develop novel ultramicroporous chiral MOFs for efficient C2H2 uptake and C2H2/CO2 separation.
• To investigate the impact of reticular synthesis on MOF performance for gas separation.

Main Methods:

• Reticular synthesis of isostructural ultramicroporous chiral MOFs, MOF-NH2 and MOF-OH, by incorporating amino and hydroxy functionalities.
• Gas adsorption measurements to determine C2H2 uptake and C2H2/CO2 selectivity using Ideal Adsorbed Solution Theory (IAST).
• Multicycle breakthrough experiments and Density Functional Theory (DFT) calculations to validate separation efficiency and understand adsorption mechanisms.

Main Results:

• MOF-OH achieved a record C2H2 storage density of 0.81 g mL-1 at ambient conditions.
• MOF-OH demonstrated an IAST selectivity of 25 for C2H2/CO2, nearly double that of MOF-NH2.
• Both MOFs exhibited remarkably low adsorption enthalpies for C2H2 (16.7-17.5 kJ mol-1), among the lowest for efficient rigid C2H2 sorbents.
• MOF-OH showed excellent hydrothermal stability (surviving boiling water for 1 week) and scalability.

Conclusions:

• Reticular manipulation of organic components in MOFs is a viable strategy for enhancing C2H2/CO2 separation.
• MOF-OH presents a promising material for industrial acetylene capture and separation due to its high performance, stability, and scalability.