Cation exchange in an anionic metal-organic framework enhancing propylene/propane separation

Highly selective adsorptive separation of propylene/propane (C3H6/C3H8) using metal-organic frameworks (MOFs) is a promising approach to reducing energy consumption in the chemical industry. Here, we report a 3D anionic MOF obtained by the exchange of dimethylamine cations with small K+ ions. 77 K N2 isotherms proved that the pore volume increased from 0.30 cm3 g-1 to 0.42 cm3 g-1 after ion exchange. Moreover, at near room temperatures (273 K and 298 K), both single-component gas adsorption capacity and selectivity of C3H6/C3H8 were enhanced. The C3H6/C3H8 separation potential was further confirmed by breakthrough experiments with equimolar C3H6/C3H8 mixtures. Similar separation properties were also observed in ethylene/ethane separation. Exchanging dimethylamine cations with smaller K+ ions in an anionic MOF can significantly increase the pore volume and provide preferable interactions for C3H6, resulting in improved adsorption capacity and selectivity of C3H6/C3H8.