Pore engineering for one-step ethylene purification from a three-component hydrocarbon mixture

Ethylene production from C2 hydrocarbon mixtures through one separation step is desirable but challenging because of the similar size and physical properties of acetylene, ethylene, and ethane. Herein, we report three new isostructural porous coordination networks (NPU-1, NPU-2, NPU-3; NPU represents Northwestern Polytechnical University) that are sustained by 9-connected nodes based upon a hexanuclear metal cluster of composition [Mn6(μ3- O)2(CH3COO)3] 6+. NPU-1/2/3 exhibit a dual cage structure that was systematically fine-tuned in terms of cage size to realize selective adsorption of C2H2 and C2H6 over C2H4. Dynamic breakthrough experiments demonstrated that NPU-1 produces ethylene in >99.9% purity from a three-component gas mixture (1:1:1 C2H2/C2H4/C2H6). Molecular modeling studies revealed that the dual adsorption preference for C2H2 and C2H6 over C2H4 originates from (a) strong hydrogen-bonding interactions between electronegative carboxylate O atoms and C2H2 molecules in one cage and (b) multiple noncovalent interactions between the organic linkers of the host network and C2H6 molecules in the second cage.