Local Structure of CPO-27-Ni Metallorganic Framework upon Dehydration and Coordination of NO

Abstract

· 8H 2 O is a 3D network that maintains crystallinity and porosity after solvent removal. A mild thermal treatment in high vacuo at 393 K removes not only water physisorbed on the walls of the structure but also water directly coordinated to the Ni(II) sites. This procedure allows us to obtain a MOF material with honeycomb structure able to strongly coordinate NO. In this contribution the characterization of CPO-27-Ni in respect to structural (EXAFS compared to XRD), vibrational (IR and Raman) and electronic (UV, XANES, and luminescence) properties is described in the case of the as prepared sample, of the dehydrated sample and after NO interaction. NO is strongly bonded at the Ni(II) sites, forming a 1:1 adduct; its presence causes large modification of the vibrational and electronic properties of the material with respect to the dehydrated one. Quantitative data considering energetic aspects (microcalorimetric measurements) are also included. The ability of H 2 O molecules to slowly displace NO from the Ni(II) sites makes this material a promising candidate for NO delivery inside biological tissues.

Fundamental Aspects of H2S Adsorption on CPO-27-Ni

“…All the reported isotherms show type I behavior in which the saturation is reached at low pressure (< 1 mbar); i.e., the suitable pressure range for natural gas purification, which Note that this value is in complete agreement with the one obtained in previous studies performed on CPO-27-Ni in presence of other probes (NO and CO 32,34 ). Independently to the strength of the interaction, the 1:1 ratio was never observed for this material.…”

“…For CPO-27-Ni in interaction with H 2 S, structural features are in good agreement with the recently reported synchrotron X-ray data at room temperature 23 , with values for lattice parameters and volume lying within 1% and 2.5%, respectively. For the three structures, the average of the Ni-O bond distance in the framework and the Ni-Ni distances are also in good agreement with experimental data from different techniques 24,32 , despite a slight overestimation. As shown in Figure 5, computed results confirm that the principal interaction is observed between the Ni atom and oxygen and sulfur, even if the molecules are tilted toward a nearby oxygen atom of the framework thus indicating a weaker secondary interaction.…”

Photo-Induced Pyridine Substitution in cis-[Ru(bpy)2(py)2]Cl2: A Snapshot by Time-Resolved X-ray Solution Scattering

“…This behavior seems to be typical of the EXAFS technique; when several neighbors of the same chemical nature are located at close distances, there is a tendency to allow such distances to converge to a common value. 11,47,50 The higher correlation among parameters occurs for R Ru-N(py) /R Ru-N(bpy) = -0.73. All other correlations are below 0.5 in absolute value.…”

Interaction of Small Molecules within Metal Organic Frameworks Studied by In Situ Vibrational Spectroscopy

“…Due to the passivation of open metal sites by hydroxyl group, the MOFs compounds lose a substantial fraction of their original gas uptake capacity. NO adsorption has been studied before in Ni, Co-MOF-74 by isotherm, X-ray diffraction infrared and Raman spectroscopy, showing that NO interacts strongly with metal centers, forming NO coordination adduct with a binding energy of 90-92 kJ/mol [19,20]. Infrared spectra shows that the stretching band ν(NO) of adsorbed NO molecules appears at a frequency between 1845 and 1838 cm −1 as coverage increases (see Figure 8).…”