An ethane-trapping MOF PCN-250 for highly selective adsorption of ethane over ethylene

Energy-saving separation of ethane/ethene (C2H6/C2H4) mixtures is of great importance and challenge. In this work, we reported an iron-based metal–organic framework PCN-250 as a C2H6-selective adsorbent for efficient C2H4 purification from C2H6/C2H4 mixtures. Adsorption isotherms of C2H6 and C2H4 were measured and their adsorption capacities were 5.21 and 4.22 mmol/g at 298 K and 100 kPa, respectively. The adsorption selectivities of C2H6/C2H4 mixtures (1:15 and 1:1, v/v) were in the range of 1.9–4.0 on the basis of ideal adsorbed solution theory (IAST). Meanwhile, its separation performance was also corroborated by the breakthrough experiments, indicating the potential of C2H4 purification from C2H6/C2H4 mixtures, particularly for trapping C2H6 from typical cracked gas mixtures (C2H6/C2H4, 1:15). Compared with C2H4-selective adsorbents through π-complexation interactions, the isosteric adsorption heat of C2H6 on PCN-250 was much lower and thus could require less energy for desorption. Meanwhile, configurational-biased grand canonical Monte Carlo (CB-GCMC) method was employed to well simulate its adsorption behaviors in PCN-250. Simulation results showed that the favorable adsorption sites of C2H6 and C2H4 were distributed at four corners near benzene rings and around the N atoms of PCN-250. Both the pore effect and the van der Waals (vdW) adsorption energy governed the separation of C2H6 over C2H4 for PCN-250, especially at low pressures. Providing that PCN-250 is used as a C2H6-selective adsorbent for purifying C2H4 from C2H6/C2H4 mixtures, this high-performance material can hold great potential for trapping C2H6 from C2H6/C2H4 mixtures.