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

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.