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 C 2 hydrocarbons is crucial yet energy-intensive in the petrochemical industry. This work reports a novel metal–organic framework (MOF), [Zn 2 (BDPO) 0.5 (5-atz) 3 ]·2.5DMA·2H 2 O ( 1 ) (H 4 BDPO = N, N ′-bis(3,5-dicarboxyphenyl)oxalamide, 5-Hatz = 5-amino-1 H -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 C 2 H 4 from C 2 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 C 2 H 2 and C 2 H 6 over C 2 H 4 . The MOF reveals significant IAST selectivities for C 2 H 2 /C 2 H 4 (3.1) and C 2 H 6 /C 2 H 4 (1.8) from equimolar mixtures at 298 K, and efficient one-step dynamic separation from C 2 H 4 /C 2 H 6 /C 2 H 2 (8:1:1, v/v/v) ternary mixtures to produce high-purity C 2 H 4 (99.9%). Grand canonical Monte Carlo (GCMC) simulations show that the strong host–guest interactions for C 2 H 2 and C 2 H 6 within the cages from the rich N/O active sites contribute to the excellent C 2 H 4 separation ability.