A Distinct Microporous Metal–Organic Framework with Multiple Accessible Adsorption Sites for Separation of C₂H₂/CO₂/CH₄ Mixtures

Abstract

Acetylene (C₂H₂), as a crucial chemical feedstock, and its purification from multicomponent light hydrocarbon mixtures is industrially challenging. Herein, we used the 3-methyl-4-(4H-1,2,4-triazol-4-yl) benzoic acid (HL) ligand and CoSO₄·7H₂O to assemble a novel metal-organic framework (MOF), [Co₃(L)₂(OH)₂(SO₄) (H₂O)]·DMA·4H₂O (1), with porous channels decorated with accessible active sites including an open metal center, an uncoordinated carboxylate group, functional methyl groups, and sulfate anions. The adsorption capacities are 64.1, 30.3, and 9.4 cm³ g^-1 for C₂H₂, CO₂, and CH₄, respectively, with an excellent adsorption selectivity of C₂H₂/CH₄ (56.2), C₂H₂/CO₂ (5.6), and CO₂/CH₄ (6.7). During the breakthrough time intervals (Δτ) of 12.4, 3.5, and 3.3 min g^-1 for the equimolar C₂H₂/CH₄, CO₂/CH₄, and ternary C₂H₂/CO₂/CH₄ mixtures, the productivities of 50.8, 10.4, and 8.2 L kg^-1, respectively, for high purity of CH₄ (≥99.9%) can be obtained. Particularly, 10.3 L kg^-1 of C₂H₂ (>99%) was recovered by a regenerated test for the equimolar ternary C₂H₂/CO₂/CH₄ mixture. Moreover, the grand canonical Monte Carlo (GCMC) simulations revealed that the selective separation of C₂H₂, CO₂, and CH₄ mixtures is attributed to the synergistic effect from multiple accessible adsorption sites.