Boosting Acetylene Packing Density within an Isoreticular Metal-Organic Framework for Efficient C₂H₂/CO₂ Separation

Area of Science:

• Materials Science
• Chemical Engineering
• Separation Science

Background:

• Porous solid adsorbents for acetylene (C2H2)/carbon dioxide (CO2) separation face challenges like poor stability, high cost, and high regeneration energy, hindering industrial use.
• An ideal adsorbent requires a balance of low cost, high stability, scalability, and effective separation performance.
• Reticular chemistry offers a pathway to design advanced materials for specific gas separation tasks.

Purpose of the Study:

• To explore an effective strategy for C2H2/CO2 separation using modified metal-organic frameworks (MOFs).
• To investigate the impact of embedding methyl groups into a prototype MOF on separation performance and stability.
• To assess the potential of the modified MOF for industrial implementation in gas separation.

Main Methods:

• Synthesis of a methyl-functionalized microporous metal-organic framework (MOF), CAU-10-CH3, via reticular chemistry.
• Characterization of gas sorption properties using single-component gas isotherms to evaluate C2H2 packing density and C2H2/CO2 uptake differences.
• Determination of adsorption enthalpy for C2H2 and CO2.
• Validation of separation performance using dynamic column breakthrough experiments.

Main Results:

• CAU-10-CH3 demonstrated a significantly enhanced C2H2 packing density (486 g L-1) and a high C2H2/CO2 uptake difference (147%) compared to the unfunctionalized CAU-10-H (392 g L-1 and 53%).
• The methyl functionalization led to a lower C2H2 adsorption enthalpy (25.18 kJ mol-1), indicating higher selectivity for C2H2 over CO2.
• Dynamic breakthrough experiments confirmed the efficient separation of C2H2/CO2 mixtures by CAU-10-CH3.

Conclusions:

• CAU-10-CH3 achieves a superior balance of cost, stability, scalability, and separation performance for C2H2/CO2 mixtures.
• The methyl-functionalization strategy effectively enhances C2H2 adsorption and selectivity, paving the way for practical MOF applications.
• This study highlights the potential of MOF materials for challenging industrial gas separation processes.