One MOF with a New Type of Layer–Pillar Structure and Candy-like Cages for One-Step Purification of C ₂ H ₄ from C ₂ Hydrocarbons

The separation of C₂ hydrocarbons is crucial yet energy-intensive in the petrochemical industry. This work reports a novel metal-organic framework (MOF), [Zn₂(BDPO)0.5(5-atz)₃]·2.5DMA·2H₂O (1) (H₄BDPO = N,N'-bis(3,5-dicarboxyphenyl)oxalamide, 5-Hatz = 5-amino-1H-tetrazole), constructed from mixed carboxylate and azolate linker with rich N/O active sites from oxalamide and amine groups in ligands, for efficient one-step purification of C₂H₄ from C₂ hydrocarbons. The MOF has the characteristic of a unique layer-pillar framework based on the metal-azolate layers pillared by BDPO linkers and possesses candy-like cages with polar porous surfaces, leading to the adsorption selectivity, higher uptake, and affinity for C₂H₂ and C₂H₆ over C₂H₄. The MOF reveals significant IAST selectivities for C₂H₂/C₂H₄ (3.1) and C₂H₆/C₂H₄ (1.8) from equimolar mixtures at 298 K, and efficient one-step dynamic separation from C₂H₄/C₂H₆/C₂H₂ (8:1:1, v/v/v) ternary mixtures to produce high-purity C₂H₄ (99.9%). Grand canonical Monte Carlo (GCMC) simulations show that the strong host-guest interactions for C₂H₂ and C₂H₆ within the cages from the rich N/O active sites contribute to the excellent C₂H₄ separation ability.