S1: Multivariate, flexible MOFs: The role of functionalized linkers, heterogeneity and defects
Roland A. Fischer
In order to understand the role of the linkers in general and functionalized linkers (fu-L) in particular on the structural flexibility and the stimuli responsiveness of MOFs, S1 focuses on the development of a library of tailored model “fu-MOFs” based on pillared layer systems exhibiting the dinuclear paddle-wheel node (M2(O2C-R)4, M = Cu, Zn; and Ni in selected cases). The project S1 complements the parallel project S2 which focusses mainly on the role of the metal ions in the nodes and keeping the linker invariant with DUT-8(Ni) as the key species. S1 uses a range of fu‐Ls which feature “orthogonal” interaction motives to derive solid solution‐type multicomponent (multivariate) fu‐MOFs with the metal ions (mainly) invariant to study the underlying effects introduced by the linkers. The objective is to achieve design, i.e. efficient “programming” of the sorption selectivity and framework flexibility. Some focus is on the gating effect in case of mixtures of adsorbents (gases and liquids, in collaboration with S2) and the involved molecular host/guest interactions (specific vs. non‐specific responsivity). The role of structural defects and disorder/heterogeneity is studied. Detailed characterization is targeted for selected cases by employing tailored in situ techniques such as X‐ray diffraction (S2), EPR (P1) and solid state NMR (P2). Feedback into experimental design (choice of fu-Ls for single und multicomponent synthesis) is obtained from theoretical modelling (T1, T2) including the development of scale bridging techniques.
Fig. 1. Representation of the single-crystal structure of the fu-MLP [Zn2(2,5-PE)2(dabco)] (PE = CH3(CH2)4O- = pentyloxy) viewed along the [001] direction. O and N atoms are depicted in red and green, respectively. Zn coordination polyhedra are shown in blue. Individual PE-bdc linkers are represented in dark green, aqua, orange and purple (without distinguishing between C and O).
S. Wannapaiboon, A. Schneemann, I. Hante, M. Tu, K. Epp, A.-L. Semrau, C. Sternemann, M. Paulus, G. Kieslich, R. A. Fischer, “Control of Structural Flexibility of Layered-Pillared Metal-Organic Frameworks Anchored at Surfaces”, Nat. Comm. 2019, 10(1), 346.
M. Mendt, P. Vervoorts, A. Schneemann, R. A. Fischer, A. Pöppl, “Probing Local Structural Changes at Cu2+ in a Flexible Mixed-Metal MOF by In Situ EPR during CO2 Ad-and Desorption”, J. Phys. Chem. C, 2019, 123(5), 2940-2952.
S. Dissegna, P. Vervoorts, C. L. Hobday, T. Düren, D. Daisenberger, R. A. Fischer, G. Kieslich, “Tuning the Mechanical Response of Metal-Organic Frameworks by Defect Engineering”, J. Am. Chem. Soc. 2018, 140, 11581–11584.
A. Schneemann, P. Vervoorts, I. Hante, M. Tu, S. Wannapaiboon, C. Sternemann, M. Paulus, D. C. Florian W., S. Henke, R. A. Fischer, “Different Breathing Mechanisms in Flexible Pillared-Layered Metal-Organic Frameworks: Impact of the Metal Center”, Chem. Mater. 2018, 30, 1667-1676.