Predicting the Features of Methane Adsorption in Large Pore Metal-Organic Frameworks for Energy Storage

Abstract

Currently, metal-organic frameworks (MOFs) are receiving significant attention as part of an international push to use their special properties in an extensive variety of energy applications. In particular, MOFs have exceptional potential for gas storage especially for methane and hydrogen for automobiles. However, using theoretical approaches to investigate this important problem presents various difficulties. Here we present the outcomes of a basic theoretical investigation into methane adsorption in large pore MOFs with the aim of capturing the unique features of this phenomenon. We have developed a pseudo one-dimensional statistical mechanical theory of adsorption of gas in a MOF with both narrow and large pores, which is solved exactly using a transfer matrix technique in the Osmotic Ensemble (OE). The theory effectively describes the distinctive features of adsorption of gas isotherms in MOFs. The characteristic forms of adsorption isotherms in MOFs reflect changes in structure caused by adsorption of gas and compressive stress. Of extraordinary importance for gas storage for energy applications, we find two regimes of Negative gas adsorption (NGA) where gas pressure causes the MOF to transform from the large pore to the narrow pore structure. These transformations can be induced by mechanical compression and conceivably used in an engine to discharge adsorbed gas from the MOF. The elements which govern NGA in MOFs with large pores are identified. Our study may help guide the difficult program of work for computer simulation studies of gas storage in MOFs with large pores.

Exploring the thermodynamic criteria for responsive adsorption processes

“…For NGA to occur, this value of Ω crit is vital and represents a delicate balance between kinetics and thermodynamic driving forces. We note, a recent study was also able to describe NGA using a transfer matrix technique 34. However, this considered a system in equilibrium, which cannot capture metastability.…”

Densification-Induced Structure Changes in Basolite MOFs: Effect on Low-Pressure CH4 Adsorption

“…Among them, mechanical compression is an inexpensive procedure and avoids the use of additional components like polymeric binders, which may change the physical properties of MOFs [ 31 ]. However, compression pelletization could also induce amorphization as well as phase transformations, which could influence also the adsorption capacities of the MOFs [ 32 , 33 ].…”

Preparation of Magnetic Fe3O4/MIL-88A Nanocomposite and Its Adsorption Properties for Bromophenol Blue Dye in Aqueous Solution

“…MOFs are a class of crystalline materials made by linking metal clusters or ions and organic linkers through covalent bonds. Owing to their highly ordered structures, high porosity and large surface areas, MOFs have attracted intensive attention in gas storage [15], molecular sensing [16], catalysis [17], energy [18], and water remediation [14]. Recently, many kinds of MOF-based materials such as rod-like metal-organic framework nanomaterial and MOF composites have been successfully synthesized and are widely used to remove dyes from wastewater [19,20,21,22].…”