A Microporous Metal-Organic Framework with Unique Aromatic Pore Surfaces for High Performance C₂ H₆ /C₂ H₄ Separation

Area of Science:

• Materials Science
• Chemical Engineering
• Separation Science

Background:

• Energy-intensive cryogenic distillation is the standard for separating ethylene from ethane.
• Developing selective sorbents for adsorptive separation presents a promising, energy-efficient alternative.
• Challenges remain in achieving high selectivity and capacity for C2H6/C2H4 mixtures.

Purpose of the Study:

• To investigate and compare the performance of two isostructural metal-organic frameworks (Ni-MOF 1 and Ni-MOF 2) for C2H6/C2H4 separation.
• To identify the structural and chemical features responsible for selective ethane adsorption.
• To evaluate the potential of these materials as alternatives to cryogenic distillation for ethylene purification.

Main Methods:

• Synthesis and characterization of two isostructural metal-organic frameworks (Ni-MOF 1 and Ni-MOF 2).
• Gas sorption isotherm measurements to determine adsorption capacities and selectivities.
• Breakthrough experiments to assess real-time separation performance.
• Density-Functional Theory (DFT) calculations to understand adsorption mechanisms.

Main Results:

• Ni-MOF 2 exhibited significantly higher C2H6/C2H4 separation performance compared to Ni-MOF 1.
• DFT studies revealed that unique aromatic pore surfaces in Ni-MOF 2 enhance C-H···π interactions with C2H6.
• Ni-MOF 2 demonstrated excellent C2H6 uptake capacity and selectivity, producing 12 L/kg of polymer-grade C2H4 from equimolar mixtures at ambient conditions.

Conclusions:

• Ni-MOF 2 is identified as a highly effective porous material for C2H6/C2H4 separation.
• The material's unique pore structure and interactions facilitate superior ethane selectivity.
• This research highlights Ni-MOF 2 as a promising candidate for developing advanced adsorptive separation processes, potentially replacing energy-intensive distillation.