Recent advances and potential applications of flexible adsorption and separation materials: A review

Abstract

In adsorption processes of the liquid or gas phase, a particular dynamic adsorption behavior caused by the reversible mechanical deformation (expansion or contraction) of absorption materials driven by the host–guest interaction is called “flexible adsorption,” and the materials with this particular behavior can be called “flexible adsorption materials.” Flexible absorption materials, such as crosslinked polymers, have received much attention from researchers due to their flexible framework structure and specific adsorption kinetics. They have shown great potential in gas storage and other energy applications. This paper reviews recent advances in the definition, theoretical development, and classification of flexible absorption materials. Potential application examples of flexible absorption materials in gas/liquid absorption and separation, functional devices, and energy catalysis are analyzed to guide their development.

Gate-opening Induced by C8 Aromatics in a Double Diamondoid Coordination Network

“… 6 , 7 In addition, gas or vapor separation might be inherently more feasible in flexible CNs given that the structural transformation can depend on the guest molecule. 8 , 9 In some cases, flexible CNs offer the chance for enhanced molecular recognition by adapting to a specific guest, a phenomenon described as “induced fit” that has been seen to dramatic effect with respect to the energetics of binding to acetylene. 10 , 11 Further, the enthalpy values of adsorption of flexible CNs can be significantly lower than those of rigid CNs due to the phase transitions, therefore mitigating the exothermic nature of adsorption.…”

“…When gate-opening/closing is reversible it is of practical interest as it can mitigate some of the drawbacks of rigid CNs, e.g., by offering higher working capacity and thermal management in gas storage and separations . Such CNs tend to exhibit characteristic “S-shaped” isotherms at a threshold pressure concomitant with gate-opening. , In addition, gas or vapor separation might be inherently more feasible in flexible CNs given that the structural transformation can depend on the guest molecule. , In some cases, flexible CNs offer the chance for enhanced molecular recognition by adapting to a specific guest, a phenomenon described as “induced fit” that has been seen to dramatic effect with respect to the energetics of binding to acetylene. , Further, the enthalpy values of adsorption of flexible CNs can be significantly lower than those of rigid CNs due to the phase transitions, therefore mitigating the exothermic nature of adsorption . Nevertheless, there remains a dearth of information on flexibility in the context of gas or vapor separation that is compounded because pure gas/vapor isotherms do not always translate well to multicomponent mixtures.…”