Guest Cation Functionalized Metal Organic Framework for Highly Efficient C₂H₂/CO₂ Separation

Area of Science:

• Materials Science
• Chemical Engineering
• Separation Science

Background:

• Separating carbon dioxide (CO2) from acetylene (C2H2) is challenging due to similar properties.
• Existing metal-organic frameworks (MOFs) for C2H2/CO2 separation have limited design strategies.
• Pore modification in MOFs offers potential for enhanced gas adsorption and molecular recognition.

Purpose of the Study:

• To develop a novel guest cation functionalization strategy for MOFs.
• To improve acetylene uptake and separation from carbon dioxide using modified MOFs.
• To investigate the molecular recognition mechanism in functionalized MOFs.

Main Methods:

• Utilized an anionic framework SU-102 as the prototype material.
• Introduced lithium cations (Li+) into the framework via ion exchange to create SU-102-Li+.
• Employed ideal adsorbed solution theory (IAST) selectivity calculations and dynamic breakthrough experiments.

Main Results:

• SU-102-Li+ demonstrated significantly enhanced C2H2 uptake (49.18 cm3 g-1) and CO2 uptake (29.88 cm3 g-1).
• Achieved a 20.3% improvement in C2H2 uptake and a 36.9% improvement in CO2 uptake compared to the parent material.
• Confirmed superior and stable C2H2/CO2 separation performance with a selectivity of 25 min g-1 and C2H2 productivity of 1.55 mmol g-1.

Conclusions:

• Guest cation functionalization is an effective strategy for enhancing MOF performance in gas separation.
• SU-102-Li+ exhibits excellent potential for industrial C2H2/CO2 separation processes.
• Theoretical calculations elucidated the specific molecular interactions driving the enhanced separation.