Sieving Effect for the Separation of C₂ H₂ /C₂ H₄ in an Ultrastable Ultramicroporous Zinc-Organic Framework

The separation of C₂ H₂ from C₂ H₄ is one of the most challenging tasks due to the similarity of their physical properties. In addition, green synthetic protocol and adsorbent's stability are also the major concerns during the separation. Herein, under hydrothermal green synthesis conditions, an ultrastable ultramicroporous Zn-MOF was designed and synthesized with a high yield. The pore diameter of the Zn-MOF is 3.6 Å, which lies in between the diameters of C₂ H₂ (3.3 Å) and C₂ H₄ (4.2 Å) molecules, leading to an efficient separation of the C₂ H₂ /C₂ H₄ mixtures by the sieving effect. The practical separation performance of C₂ H₂ /C₂ H₄ was confirmed by the dynamic breakthrough experiments. Moreover, the high stability enables the adsorption capacity of the Zn-MOF to C₂ H₂ , which can be maintained under a wide range of pH (1-13). Molecular simulations were also performed to identify the different C₂ H₂ - and C₂ H₄ -binding sites in Zn-MOF.