Acetylene Storage and Separation Using Metal–Organic Frameworks with Open Metal Sites

Abstract

Efficient separation and storage of gas streams involving light hydrocarbons is essential for industrial applications. These hydrocarbons are widely used as energy resources and/or chemical raw materials in various chemical reactions. Here, we focus on the separation of acetylene from methane and carbon dioxide. The separation of acetylene from carbon dioxide is, in particular, challenging due to the similar kinetic diameters and boiling points of the molecules. In recent years, considerable progress has been made in adsorption-based separations using porous metal−organic frameworks (MOFs). Most reported studies are experimental. We present a computational study on these gas separations using a variety of MOFs. This allows investigation of the competitive gas adsorption, which is experimentally challenging, as well as understanding the adsorption mechanisms at the molecular level, which in turn allows further experimental MOF design for this application. MOFs with open metal sites, and particularly Fe-MOF-74, seem to be good for this separation, with a trade-off between physical adsorption capacity and selectivity. Based on experimental single-adsorption isotherms at various temperatures, we developed and validated a specific parameterization to account for the interactions of the olefin with the open metal sites. In addition to volumetric and calorimetric adsorption, we comprehensively investigate the characteristics of the interaction between the MOFs and the guest molecules in terms of binding sites and density profiles. The overall agreement of our simulated results with experimental data for pure components points to the reliability of the models and methods to successfully predict the separation of mixtures.

One‐step Ethylene Purification from an Acetylene/Ethylene/Ethane Ternary Mixture by Cyclopentadiene Cobalt‐Functionalized Metal–Organic Frameworks

“…[29] It is relatively simple to introduce metal ions into the porphyrin center (Figure 2b), but the disadvantage is that this significantly enhances the effect on C 2 H 4 . [30] It has been shown that C 2 H 6 can be stabilized in the pores through intermolecular dipolar and supramolecular interactions with the aromatic ligands. [31][32][33] Herein, we describe an ew modification, introduction of cyclopentadiene cobalt into the linker based on the stable ftw topology platform (Figure 1b and 2c), together with al ayer of cyclopentadiene wrapped on the outer side of cobalt to selectively increase the force associated with C 2 H 2 and C 2 H 6 .O no ne hand, cyclopentadiene-cobalt can increase the weak interaction with C 2 H 2 and C 2 H 6 and on the other hand, it can further divide the space in the cage to form asphere-like force surface (Figure 2f).…”

One‐step Ethylene Purification from an Acetylene/Ethylene/Ethane Ternary Mixture by Cyclopentadiene Cobalt‐Functionalized Metal–Organic Frameworks

“…The traditional modification methods are to expose the metal sites, for example by removal of the coordinated solvent by activation [27, 28] or to directly introduce the metal sites into the linker [29] . It is relatively simple to introduce metal ions into the porphyrin center (Figure 2 b), but the disadvantage is that this significantly enhances the effect on C 2 H 4 [30] . It has been shown that C 2 H 6 can be stabilized in the pores through intermolecular dipolar and supramolecular interactions with the aromatic ligands [31–33] .…”

Molecularly Imprinted Porous Aromatic Frameworks for Molecular Recognition

“… 27 , 28 (2) MOF samples are gifted with open metal sites that can strongly interact with guest molecules such as hydrogen and acetylene. 29 − 33 Therefore, they could potentially be capable of separating gas molecules and sensing neutral and ionic species. However, these materials have many drawbacks, such as low selectivity, complicated synthesis procedures, and limited universality.…”

“…(b) Acetylene separation based on metal–organic frameworks with open metal sites. Reprinted with permission from ref ( 29 ). Copyright 2019, American Chemical Society.…”