A polyhedron-based metal-organic framework with electronegative donor sites for efficient C2H6/C2H4 separation

Ethylene is an important chemical raw material which is widely used in the production of chemical fibers, plastics, rubber, coatings, as well as medicines, and its separation from the gas mixtures of C 2 H 6 /C 2 H 4 is of great importance but a challenging task due to their similar physical properties and molecular dimensions. Herein, we report the C 2 H 6 and C 2 H 4 sorption studies on a robust anionic metal-organic framework (MOF) {(NH 2 Me 2 )[Co 3 (μ 3 OH)(TPT)(TZB) 3 ](H 2 O) 6 (DMA) 6 } n (Co-MOF) formed by connection of Co 3 (OH) clusters by two N-rich organic ligands 2,4,6-tri(4-pyridyl)-1,3,5-triazine (TPT) and 4-(1H-Tetrazol-5-yl)benzoic acid (H 2 TZB). The prepared Co-MOF features a polyhedron stacking network structure composed of trigonal bipyramidal cages and octahedral cage which both contribute to a high C 2 H 6 uptake capacity of 6.48 mmol/g and a decent C 2 H 6 /C 2 H 4 selectivity of 1.54 at 298 K and 1 bar. Grand Canonical Monte Carlo (GCMC) simulation results agree well with the experimental tendency, both in the adsorption isotherms and sorption heats, which demonstrated that the suitable pore surfaces with electronegative donor sites generated multiple C H ⋅⋅⋅O/N and C H ⋅⋅⋅π interactions between the framework and C 2 H 6 , resulting in a stronger interaction between the MOF skeleton and C 2 H 6 molecule than C 2 H 4 as reflected by the dispersion-corrected density functional theory (DFT) calculation.