CH₄ Purification by a Carborane-Based Metal-Organic Framework with Rare Tetranuclear Copper Nodes.

Area of Science:

• Materials Science
• Chemical Engineering
• Separation Science

Background:

• Efficient methane (CH4) purification is critical for natural gas utilization.
• Adsorptive separation using porous metal-organic frameworks (MOFs) is an energy-efficient strategy.
• Existing MOFs often face challenges in selectively separating methane from other hydrocarbons.

Purpose of the Study:

• To synthesize and characterize a novel carborane hybrid MOF for methane purification.
• To investigate the adsorption and separation performance of the synthesized MOF for C2/C3 hydrocarbons and methane.
• To elucidate the separation mechanism and confirm its practical applicability in natural gas upgrading.

Main Methods:

• Solvothermal synthesis of the carborane hybrid MOF (Cu-CB-DMTPA).
• Gas adsorption experiments at 298 K and 1.0 bar.
• Ideal Adsorbed Solution Theory (IAST) selectivity calculations.
• In situ single-crystal X-ray diffraction (SCXRD) and Grand Canonical Monte Carlo (GCMC) simulations.
• Dynamic breakthrough experiments using a CH4/C2H6/C3H8 mixture.

Main Results:

• Cu-CB-DMTPA exhibits electronegative pore surfaces and dual-sized 1D channels.
• High adsorption uptake for C3H8 (29.9 cm3 g-1) and C2H6 (31.3 cm3 g-1) over CH4 (9.9 cm3 g-1).
• Exceptional IAST selectivities for C3H8/CH4 (61.2) and C2H6/CH4 (14.4).
• Dynamic breakthrough confirmed >99.99% CH4 purity with high productivity (81.53 L kg-1).
• The material shows excellent recyclability and humidity resistance.

Conclusions:

• Cu-CB-DMTPA demonstrates superior performance for selective C2/C3 hydrocarbon adsorption over methane.
• The separation mechanism involves cooperative weak interactions between the framework and hydrocarbons.
• This novel MOF shows significant potential for industrial natural gas upgrading and methane purification.