Dynamic Entangled Porous Framework for Hydrocarbon (C2-C3) Storage, CO2 Capture, and Separation

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Small hydrocarbon (C1-C3) storage and separation are crucial for energy resources and industrial materials.
• Selective carbon dioxide (CO2) capture from methane (CH4) is vital for natural gas purification.
• Metal-organic frameworks (MOFs) with permanent porosity are promising for gas separation and storage.

Purpose of the Study:

• To exploit a two-fold entangled dynamic framework for selective capture of CO2, C2, and C3 hydrocarbons.
• To investigate the adsorption behavior of the framework at different temperatures.
• To evaluate the framework's performance in separating gas mixtures relevant to natural gas and greenhouse gas mitigation.

Main Methods:

• Synthesis and characterization of a novel dynamic metal-organic framework {[Zn2 (bdc)2 (bpNDI)]⋅4DMF}n.
• Gas adsorption isotherms measured at 195 K and 298 K.
• Ideal Adsorbed Solution Theory (IAST) calculations for selectivity.
• Density Functional Theory (DFT) for understanding adsorption mechanisms.
• Breakthrough column experiments for practical separation evaluation.

Main Results:

• The framework exhibits stepwise CO2 and C2H2 uptake at 195 K and Type I profiles at 298 K.
• Achieved the highest reported CO2/CH4 selectivity (598) at 298 K for MOFs without open metal sites.
• Demonstrated high selectivity for C2H2, C2H4, C2H6, and C3H8 over CH4 at 298 K.
• DFT calculations identified aromatic π surfaces and polar imide groups as key adsorption sites.
• Successful separation of CO2/CH4, C2H6/CH4, and CO2/N2 mixtures in breakthrough experiments at ambient conditions.

Conclusions:

• The dynamic framework is highly effective for selective CO2 and C2/C3 hydrocarbon capture at ambient conditions.
• The material's unique pore surface chemistry (aromatic π and polar imide groups) drives selective adsorption.
• This MOF presents a promising solution for natural gas upgrading and carbon capture technologies.