Fine-Tuning MOFs with Amino Group for One-Step Ethylene Purification from the C2 Hydrocarbon Mixture

Due to the similar kinetic diameters of C2H2, C2H4, and C2H6, one-step purification of C2H4 from a ternary C2H2/C2H4/C2H6 mixture by adsorption separation is still a challenge. Based on a C2H6-trapping platform and crystal engineering strategy, the N atom and amino group were introduced into NTUniv-58 and NTUniv-59, respectively. Gas adsorption testing of NTUniv-58 showed that both the C2H2 and C2H4 uptake capacities and the C2H2/C2H4 separation ability were boosted compared with the original platform. However, the C2H4 uptake value exceeds the C2H6 adsorption data. For NTUniv-59, the C2H2 uptake at low pressure increased and the C2H4 uptake decreased; thus, the C2H2/C2H4 selectivity was enhanced and the one-step purification of C2H4 from a ternary C2H2/C2H4/C2H6 mixture was realized, which was supported by the enthalpy of adsorption (Qst) and breakthrough testing. Grand canonical monte carlo (GCMC) simulation indicated that the preference for C2H2 over C2H4 originates from multiple hydrogen-bonding interactions between amino groups and C2H2 molecules.