Abstract
Soft porous crystals (SPCs) are widely known for their intriguing properties and various counterintuitive phenomena such as negative linear compression, negative thermal expansion and negative gas adsorption (NGA). An intriguing case is the adsorption of methane in DUT-49 for which experimentally a drop in the amount of adsorbed particles was observed under increasing vapor pressure. It is yet unknown which specific systems can exhibit NGA under which thermodynamic conditions. Herein, a semi-analytical thermodynamic model is applied to determine the conditions required for NGA, including their sensitivity towards various system-specific parameters, and investigate the correlation with pressure-induced breathing. As such, it is found that certain non-breathing materials may exhibit breathing with NGA under application of a fixed mechanical pressure. Such meticulous control of multiple triggers for NGA can open the way to new applications such as tunable gas detection and pressure amplification.
Highlights
Soft porous crystals (SPCs) are widely known for their intriguing properties and various counterintuitive phenomena such as negative linear compression, negative thermal expansion and negative gas adsorption (NGA)
Even though flexibility and crystallinity are usually perceived as counterintuitive, it was discovered that some Metal–organic frameworks (MOFs) show “flexible” behavior in the sense that they are capable of transforming between various phases accompanied by substantial changes in the unit cell volume while retaining their structural integrity
Evans et al investigated the structural transition in more detail using molecular dynamics simulations and found that a molecular buckling of the organic linker results in a colossal framework transformation that allows for negative gas adsorption[24]
Summary
Soft porous crystals (SPCs) are widely known for their intriguing properties and various counterintuitive phenomena such as negative linear compression, negative thermal expansion and negative gas adsorption (NGA). An intriguing case is the adsorption of methane in DUT49 for which experimentally a drop in the amount of adsorbed particles was observed under increasing vapor pressure. It is yet unknown which specific systems can exhibit NGA under which thermodynamic conditions. Krause et al found that DUT–48, a new material they synthesized which is very similar to DUT–49 but with a smaller linker, does not exhibit any breathing transitions and as a result, no NGA27 They found that a stiffening of the framework (due to the smaller linker) with respect to DUT–49, in combination with a lower adsorption enthalpy of methane was responsible for the lack of transitions. It was found that the particle size alters the complex structural transformation mechanism and yields multiple structural transformations figuring unprecedented intermediate structures
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
