Angeli Giasemi K, Loukopoulos Edward, Kouvidis Konstantinos, Bosveli Artemis, Tsangarakis Constantinos, Tylianakis Emmanuel, Froudakis George, Trikalitis Pantelis N
Department of Chemistry, University of Crete, Voutes, 71003 Heraklion, Greece.
J Am Chem Soc. 2021 Jul 14;143(27):10250-10260. doi: 10.1021/jacs.1c03762. Epub 2021 Jun 29.
Guest responsive porous materials represent an important and fascinating class of multifunctional solids that have attracted considerable attention in recent years. An understanding of how these structures form is essential toward their rational design, which is a prerequisite for the development of tailor-made materials for advanced applications. We herein report a novel series of stable rare-earth (RE) MOFs that show a rare continuous breathing behavior and an unprecedented gas-trapping property. We used an asymmetric 4-c tetratopic carboxylate-based organic ligand that is capable of affording highly crystalline materials upon controlled reaction with RE cations. These MOFs, denoted as RE--MOF-1 (RE: Y, Sm, Eu, Tb, Dy, Ho, and Er), feature hexanuclear RE clusters that display a highly unusual connectivity and serve as unique 8-c hemi-cuboctahedral secondary building block, resulting in a new (3,3,8)-c topology. Extensive single-crystal to single-crystal structural analyses coupled with detailed gas (N, Ar, Kr, CO, CH, and Xe) and vapor (EtOH, CHCN, CH, and CH) sorption studies, supported by accurate theoretical calculations, shed light onto the unique swelling behavior. The results reveal a synergistic action involving steric effects, associated with coordinated solvent molecules and 2-fluorobenzoate (2-FBA) nonbridging ligands, as well as cation-framework electrostatic interactions. We were able to probe the individual role of the coordinated solvent molecules and 2-FBA ligands and found that both cooperatively control the gas-breathing and -trapping properties, while 2-FBA controls the vapor adsorption selectivity. These findings provide unique opportunities toward the design and development of tunable RE-based flexible MOFs with tailor-made properties.
客体响应性多孔材料是一类重要且迷人的多功能固体材料，近年来受到了广泛关注。了解这些结构的形成方式对于其合理设计至关重要，而合理设计是开发用于先进应用的定制材料的先决条件。我们在此报告了一系列新型的稳定稀土（RE）金属有机框架材料（MOF），它们表现出罕见的连续呼吸行为和前所未有的气体捕获特性。我们使用了一种基于不对称四齿羧酸酯的有机配体，该配体在与稀土阳离子进行可控反应时能够生成高度结晶的材料。这些MOF被命名为RE-MOF-1（RE：Y、Sm、Eu、Tb、Dy、Ho和Er），其特征是具有六核稀土簇，这些簇显示出高度不寻常的连接性，并作为独特的8连接半立方八面体二级结构单元，从而形成了一种新的（3,3,8）连接拓扑结构。广泛的单晶到单晶结构分析，结合详细的气体（N₂、Ar、Kr、CO、CH₄和Xe）和蒸汽（EtOH、CH₃CN、CH₂Cl₂和CH₃OH）吸附研究，并辅以精确的理论计算，揭示了这种独特的膨胀行为。结果表明，协同作用涉及空间效应，这与配位溶剂分子和2-氟苯甲酸酯（2-FBA）非桥连配体有关，以及阳离子-框架静电相互作用。我们能够探究配位溶剂分子和2-FBA配体的各自作用，发现它们共同控制气体呼吸和捕获特性，而2-FBA控制蒸汽吸附选择性。这些发现为设计和开发具有定制特性的可调谐稀土基柔性MOF提供了独特的机会。
