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

某些多孔金属-有机框架（MOFs）的一个迷人的特性是它们的刺激诱导呼吸，这是纳米多孔吸附剂领域与其他参比材料（如活性炭和沸石）相比的独特特征。最近，德累斯顿工业大学（TUD）发现了一种新的呼吸MOF，即DUT 49，在客人吸附时显示出一种特殊的反直觉现象，即所谓的负气体吸附，导致中孔框架在排出的气体量和压力增加方面的巨大响应。除了由与超过50%的晶胞体积变化相关的大规模结构转变引发的这种有趣现象的基本兴趣之外，在机械致动器方面存在许多可能的技术应用，这些机械致动器选择性地对环境压力的变化做出反应，并且能够将大量的潜在应变转化为压力。FUN的高度挑战性目标是（i）系统地研究这种MOF框架的化学官能化的影响，即金属和有机连接剂的性质（不同长度和官能团），对NGA响应的影响（排出的气体量、压力阈值、压力放大）和MOF框架的相关变化，（ii）通过结合模拟、量热测量和原位结构分析，深入了解在NGA现象的起源处控制DUT 49的客致结构收缩的驱动力，（iii）预期改进的DUT 49，并进一步展示其主要在高压放大方面的最佳NGA性能，以及（iv）最后提出一个新的概念，先进的仪器开发与潜在的合作伙伴在一个更应用的项目在第二阶段。这个跨学科的项目要求在高质量MOF样品的合成/表征，先进的吸附，能量和结构方法，以及最先进的分子模拟，在呼吸MOF中NGA现象的筛选，理解和优化的所有阶段中高度相互关联的活动。为了解决这些极具挑战性的目标，FUN汇集了三个高度专业化的团队，他们具有互补的专业知识，包括MOF合成/结构/吸附（TUD），实验吸附/微量热法（MADIREL，马赛），实验分子动力学探索和原位高压结构表征（Institut Charles Gerhardt Montpellier ICGM）和建模（ICGM）。

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).