Simultaneous extraction of C3H8 and C2H6 from ternary C3H8/C2H6/CH4 mixtures in an ultra-microporous metal–organic framework

The efficient purification of methane from other light hydrocarbons is of prime importance in natural gas purification. However, the exploitation of stable adsorbents with both high selectivity and high adsorption capacity remains a challenge. Herein, an ultra-microporous Co-based metal–organic framework (Co-MOF) with abundant selective binding sites decorating the pore wall was applied for the highly efficient separation of ternary C3H8/C2H6/CH4 mixtures. The Co-MOF shows remarkable C3H8 and C2H6 adsorption capacities with uptakes of 59.4 cm3/g and 58.6 cm3/g, respectively, while only adsorbing a low amount of CH4 with an uptake of 16.6 cm3/g at 298 K and 100 kPa. The ideal adsorbed solution theory selectivities for C2H6/CH4 (v/v = 50/50) and C3H8/CH4 (v/v = 50/50) reach 26.0 and 290.0 at 298 K, respectively, surpassing most of the state-of-the-art MOF materials. The molecular simulation reveals that the excellent adsorption and separation performance of Co-MOF derives from its suitable pore size and functional pore surfaces. Furthermore, the breakthrough experiments reveal that the Co-MOF exhibits excellent separation performance of C3H8 and C2H6 from natural gas. Notably, the dynamic separation performance of Co-MOF can be well-maintained after five cycles, demonstrating its excellent cycling stability. The high stability and excellent separation performance make Co-MOF a promising adsorbent for natural gas purification.