Multivariate, flexible MOFs: The role of functionalized linkers, heterogeneity and defects

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Based on the collaboratively obtained results in FOR 2433 during the 1st period, the project S1 will primarily focus on research questions related to materials functions, namely on QF2 the design, synthesis and characterization of switchable catalysts catG@MOF in the 2nd period of funding. The notation catG refers to a catalytically active guest, which includes structurally defined molecular catalyst (established from homogeneous catalysis) as well as surfactant stabilized metal nanoparticles. The underlying research question (QP3) is how defects, disorder and heterogeneity will influence the responsive behavior of the parent flexible MOFs. Therefore S1 will also study the more general effects of inclusion of defG, which denotes defect generating but catalytically inactive guests (for example, nanoscale polystyrene and silica beads etc.). Addressing QF2, however, requires flexible MOF candidates, which show a switching behavior under multicomponent conditions in the solid/liquid and as well in the solid/gas situation (QF1 which is based on the knowledge about QP4, specific vs. non specific adsorption/switching). These mixed adsorption phenomena will be studied on a selection of flexible MOFs made available by S1 and S2. A second, however related work package will deal with the elucidation of the mechanistic origin of the ultrahigh kinetic selectivity in light hydrocarbon adsorption at special polymorphs of the fu-MOF family, namely the honeycomb net structures [Zn2(fu-bdc)2(bipy)] system. This fu-MOF features a rigid framework and does not undergo a phase transition during guest uptake/release. However, in case of C3 functional alkylether side groups -OR (R: propyl, vinyl, propinyl) at the bdc backbone we observed spectacular selective adsorption of propene over propane and propyne. A combined time–resolved multicomponent gas/solid adsorption study (including break-through experiments with S2) and solid-state NMR study (using deuterated hydrocarbon guest molecules with P1) will be performed together with theoretical modeling (e.g. mobility and diffusion, T2).