Highly Efficient Separation of CH4/C2H6/C3H8 from Natural Gas on a Novel Copper-Based Metal–Organic Framework

The separation of light hydrocarbons like methane, ethane, and propane is an important section of the chemical industry. Herein, we reported a novel porous metal–organic framework (MOF) Cu-IPA and investigated its CH4/C2H6/C3H8 separation performance, particularly for efficient capture of C2H6 and C3H8 at low concentrations. Cu-IPA featured 1D hexagonal channels and triangular channels decorated with extensive oxygen atoms. It showed high C2H6 and C3H8 capacities in the low-pressure region, where C3H8 uptake at 5 kPa was 1.62 mmol/g and C2H6 uptake reached 1.33 mmol/g at 10 kPa, suggesting the strong adsorption affinities toward C2H6 and C3H8. For an equimolar C2H6/CH4 mixture, Cu-IPA exhibited a considerable IAST selectivity of 40, exceeding most reported MOF adsorbents. Excellent CH4/C2H6/C3H8 separation performance for Cu-IPA can be attributed to its appropriate pore size and abundant accessible oxygens atoms in the triangular channel. The molecular simulation revealed that Cu-IPA tended to form stronger C–H···O interactions with C2H6 and C3H8 due to the higher polarizabilities, resulting in larger interaction differences between C2H6/CH4 and C3H8/CH4. Breakthrough tests also supported the excellent dynamic separation performance and recyclability of Cu-IPA.