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The monoclinic (Ni(L)[Ni(CN)4] (L= 1,4-Bis(4-pyridyl) benzene) compound (defined as Ni-dpbz) is a flexible metal organic framework which assumes a pillared structure with layers defined by 2D Ni[Ni(CN)4]n nets and dpbz ligands as pillars. The structure features an entrapped dpbz ligand that links between the open ends of four-fold Ni sites from two neighboring chains. This arrangement results in an unusual 5-fold pseudo square-pyramid environment for Ni and a significantly long Ni-N distance of 2.369(4) Å. Using Density Functional Theory calculations, the different bonding characteristics between the 5-fold and 6-fold Ni's were determined. We found that there is weak covalent bonding between the 5-fold Ni and N in the entrapped ligand, and the 6-fold Ni-N bonds provide effective electronic conduction. The disordered dimethyl sulfoxide (DMSO) solvent molecules are not bonded to the framework. The material has a single pore with a diameter of 4.1 Å. This pore includes approximately 55% of the total free volume (based on a zero-diameter probe). The accessible pore surface area and pore volume were calculated to be 507 m2/g and 6.99 cm3/kg, respectively. The maximum amount of CO2 that can be accommodated in the pores after DMSO is removed was found to be 204 mg/g, agreeing with the results of adsorption/desorption experiments of about 220 mg/g.

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Copyright (2018) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in:

Wong-Ng, W., Williamson, I., Lawson, M., Siderus, D.W., Culp, J.T., Chen Y.S. & Li, L. (2018). Electronic Structure, Pore Size Distribution, and Sorption Characterization of an Unusual MOF, {[Ni(dpbz)][Ni(CN)4]}n, dpbz = 1,4-bis(4-pyridyl)benzene. Journal of Applied Physics, 123(24), 245105.

and may be found at doi: 10.1063/1.5025674