Fundamental Understanding of Negative Gas Adsorption in Mesoporous Solids: Towards threshold sensitive mechanical actuators

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One fascinating property of certain porous Metal-Organic Frameworks (MOFs) is their stimulus-induced breathing, a unique feature in the field of nanoporous adsorbents as compared to other reference materials such as activated carbons and zeolites. Recently, Technische Universität Dresden (TUD) discovered a novel breathing MOF, i.e. DUT49, showing an exceptional counter-intuitive phenomenon upon guest-adsorption, the so-called Negative Gas Adsorption that causes a massive response of the mesoporous framework in terms of both amount of gas expelled and pressure increase. Besides the fundamental interest of this intriguing phenomenon triggered by a massive structural transition associated with more than 50% of unit cell volume change, there are many possible technological applications in terms of mechanical actuators that react selectively to changes in environmental pressure and capable of transforming a large amount of latent strain into pressure. The highly challenging objectives of FUN are to (i) systematically investigate the impact of chemical functionalization of this MOF framework, i.e. nature of the metal and the organic linker (different lengths and functional groups), on the NGA response (amount of gas expelled, pressure threshold, pressure amplification) and the associated changes of the MOF framework, (ii) gain an in-depth understanding of the driving force that governs the guest-induced structural contraction of the DUT49s at the origin of the NGA phenomenon by combining simulations, calorimetric measurements and in situ structural analyses, (iii) anticipate refined DUT49s and further showcase their optimal NGA performances primarily in terms of high pressure amplification and (iv) finally propose a novel concept for advanced instrumentation development with potential partners in a more applied project in a second stage.This interdisciplinary project calls for highly interlinked activities in synthesis/characterization of high quality MOF samples, advanced adsorption, energetic and structure methodology, and state-of-the-art molecular simulations, during all stages of the screening, understanding and optimization of the NGA phenomena in breathing MOFs. To address these highly challenging objectives, FUN assembles three highly dedicated groups with complementary expertise comprising MOF synthesis/structure/adsorption (TUD), experimental adsorption/microcalorimetry (MADIREL, Marseille), experimental molecular dynamics exploration and in situ high-pressure structure characterization (Institut Charles Gerhardt Montpellier ICGM) and modelling (ICGM).