Graphene-inspired porous polymer network for ethane/ethylene separation and methane purification

C2H4 and CH4 are essential for industrial applications. However, contamination with other natural gases is a challenge to their utilization. Although several sorbents have been investigated, their performance remains limited. This study introduces graphene-inspired, PPN-20, a porous polymer network (PPN) capable of separating C2H6/C2H4 and purifying CH4 from a C3H8/C2H6/CH4 mixture in a single step. The ultra-microporosity of PPN-20 enables preferential C-H···π interactions with C2H6 and C3H8. As a result, PPN-20 exhibits a C2H6 and C3H8 uptake of 3.93 mmol/g and 5.98 mmol/g, respectively, at 298 K and 1 bar, representing the highest reported for any PPN. It achieves ideal adsorbed solution theory (IAST) selectivities of 2.2 for C2H6/C2H4, 368.2 for C2H6/CH4, 40.14 for C3H8/C2H6, and 294,336 for C3H8/CH4. This selectivity, to the best of our knowledge, is the highest reported for any PPN in the case of C2H6/C2H4 separation and for any sorbent in the cases of C2H6/CH4, C3H8/C2H6, and C3H8/CH4 separation. Robustness tests, including breakthrough experiments, IAST calculations, etc., demonstrate the reliability of PPN-20. Its exceptional performance is attributed to precisely engineered pore sizes that enhance the trapping of guest molecules. These results will pave the way for the design of PPNs for short-chain hydrocarbon purification. A graphene-inspired porous polymer network acts as a molecular sieve, efficiently separating ethane from ethylene and purifying methane. Its finely tuned pores deliver record selectivity, offering a new path toward cleaner and energy-efficient natural gas processing.