Monitoring adsorption-induced switching by Xe-129 NMR spectroscopy in a new metal-organic framework Ni-2(2,6-ndc)(2)(dabco)

The synthesis and structure of a new flexible metal-organic framework Ni-2(2,6-ndc)(2)(dabco) (DUT-8(Ni), DUT = Dresden University of Technology, 2,6-ndc = 2,6-naphthalenedicarboxylate, dabco = 1,4-diazabicyclo[2.2.2]octane) as well as its characterization by gas adsorption and Xe-129 NMR spectroscopy is described. The compound shows reversible structural transformation without loss of crystallinity upon solvent removal and physisorption of several gases. Xenon adsorption studies combined with Xe-129 NMR spectroscopy turn out to be favorable methods for the detection and characterization of the so-called gate-pressure effect in this novel MOF material. The linewidth and chemical shift of the Xe-129 NMR signal are shown to be very sensitive parameters for the detection of this structural transition from a narrow pore system with low porosity to a wide pore state. The transition and threshold temperature is clearly detected.