Synthesis of switchable MOFs for gas and liquid phase separations: Tailored model materials for understanding selectivity

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Based on the developed understanding, the project will synthesize switchable pillared layer MOFs as model systems to demonstrate highly selective separation processes in gas- and liquid phase mixture adsorption (QF1). Di-nuclear paddle-wheel (PW) complexes (M2(O2C-R)4, M = Mn, Co, Ni, Cu, Zn) acting as nodes and [1,1'-biphenyl]-4,4'-dicarboxylates (bpdc) will not only lead to expanded pore size in switchable M2(bpdc)2(dabco) materials (DUT-128) but enable the integration of more complex functional groups in the linker for key-lock type recognition and selective pore opening. The in situ analysis (QP2) of predicted (T1, T2) switching transitions will strengthen the predictive theoretical framework (PTF). 2,6-Naphthalene dicarboxylate based materials (DUT-8(M), M = Co, Ni, Cu, Zn) will be used as model systems to achieve a fundamental understanding of the role of switchability and its impact on selectivity for binary gas mixture adsorption (QP4, QF1). The DUT-8(M) family is provided to S1 for synthesizing a switchable catalyst (QF2). Their availability as rigid and flexible systems (depending on particle size) is an important basis for NMR (P1) and EPR (P2) in situ studies in the presence of gas mixtures to analyze the implication of restoring forces on the adsorbate structure. The role of the outer particle surface (shell) will be analyzed by generating core/shell model materials (DUT-8) e.g. with a rigid shell and switchable core. The switching and PW deformation in the core vs. shell is analyzed by EPR spectroscopy (P2) by integrating appropriate paramagnetic probe centers. Based on the expanded DUT-128 model systems, selective switching in solution will be used to separate larger functional guest molecules. By mimicking DNA-like base pairing interactions between linker and selected substrates we envision to demonstrate key-lock switching mechanisms, i.e. pore opening for only a single species in a complex molecule mix.