Solubility and Stability of Hexanuclear Ce(IV)–O Clusters

Stable molecular clusters are of interest for targeted deposition in porous materials. In this work, we report the discovery of two new molecular Ce–O clusters of composition [Ce6O4(OH)4(NO3)4(DMF)4(C7H4O2X)8]·(DMF)4(H2O)2 (1-X) and [Ce6O4(OH)4(H2O)6(NO3)6(C7H4O2X)6] (2-X) (X = −Cl, −CHO, and −Br). Both cluster types contain a similar hexanuclear building unit, and crystal structures were determined from single-crystal X-ray diffraction or 3D electron diffraction data and subsequent Rietveld refinements against powder X-ray diffraction (PXRD) data. The crystal structure data is complemented by results from the local structure around the cerium ions, determined by extended X-ray absorption fine structure (EXAFS) measurements in the solid state. The composition of all Ce–O clusters was confirmed by elemental analysis, NMR and IR spectroscopy. The Ce–O clusters are highly soluble, up to 101 and 136 g/L for 1-Cl and 2-Cl, respectively, in organic solvents, which strongly depends on the type of cluster and functionalization of the benzoate ligands. Moreover, the structural and compositional integrity of dissolved clusters in different solvents was established. Recrystallization of 1-Cl from dichloromethane (DCM) and Raman spectroscopy confirm the integrity of both cluster types in solution. Further examination by EXAFS measurements on the Ce K-edge of clusters containing 4-chlorobenzoate reveals that only minor changes in the cerium environment of 1-Cl are observed upon dissolution in THF, DCM, and dioxane, while the results for 2-Cl indicate a partial degradation upon dissolution. After proving the stability, a cluster solution of 1-Cl was used to impregnate the mesoporous metal–organic framework Cr-MIL-101. Extensive characterization by PXRD, inductively coupled plasma-optical emission spectroscopy, and energy-dispersive X-ray spectroscopy, as well as thermogravimetry and N2-sorption measurements, confirm the successful insertion of Ce–O clusters into the large mesoporous cages of the framework. Due to the combination of high surface area and potential catalytic activity, the Cluster@MOF materials could be of high interest for application in heterogeneous catalysis

Solubility and Stability of Hexanuclear Ce(IV)–O Clusters

Stable molecular clusters are of interest for targeted deposition in porous materials. In this work, we report the discovery of two new molecular Ce–O clusters of composition [Ce6O4(OH)4(NO3)4(DMF)4(C7H4O2X)8]·(DMF)4(H2O)2 (1-X) and [Ce6O4(OH)4(H2O)6(NO3)6(C7H4O2X)6] (2-X) (X = −Cl, −CHO, and −Br). Both cluster types contain a similar hexanuclear building unit, and crystal structures were determined from single-crystal X-ray diffraction or 3D electron diffraction data and subsequent Rietveld refinements against powder X-ray diffraction (PXRD) data. The crystal structure data is complemented by results from the local structure around the cerium ions, determined by extended X-ray absorption fine structure (EXAFS) measurements in the solid state. The composition of all Ce–O clusters was confirmed by elemental analysis, NMR and IR spectroscopy. The Ce–O clusters are highly soluble, up to 101 and 136 g/L for 1-Cl and 2-Cl, respectively, in organic solvents, which strongly depends on the type of cluster and functionalization of the benzoate ligands. Moreover, the structural and compositional integrity of dissolved clusters in different solvents was established. Recrystallization of 1-Cl from dichloromethane (DCM) and Raman spectroscopy confirm the integrity of both cluster types in solution. Further examination by EXAFS measurements on the Ce K-edge of clusters containing 4-chlorobenzoate reveals that only minor changes in the cerium environment of 1-Cl are observed upon dissolution in THF, DCM, and dioxane, while the results for 2-Cl indicate a partial degradation upon dissolution. After proving the stability, a cluster solution of 1-Cl was used to impregnate the mesoporous metal–organic framework Cr-MIL-101. Extensive characterization by PXRD, inductively coupled plasma-optical emission spectroscopy, and energy-dispersive X-ray spectroscopy, as well as thermogravimetry and N2-sorption measurements, confirm the successful insertion of Ce–O clusters into the large mesoporous cages of the framework. Due to the combination of high surface area and potential catalytic activity, the Cluster@MOF materials could be of high interest for application in heterogeneous catalysis

Solubility and Stability of Hexanuclear Ce(IV)–O Clusters

Stable molecular clusters are of interest for targeted deposition in porous materials. In this work, we report the discovery of two new molecular Ce–O clusters of composition [Ce6O4(OH)4(NO3)4(DMF)4(C7H4O2X)8]·(DMF)4(H2O)2 (1-X) and [Ce6O4(OH)4(H2O)6(NO3)6(C7H4O2X)6] (2-X) (X = −Cl, −CHO, and −Br). Both cluster types contain a similar hexanuclear building unit, and crystal structures were determined from single-crystal X-ray diffraction or 3D electron diffraction data and subsequent Rietveld refinements against powder X-ray diffraction (PXRD) data. The crystal structure data is complemented by results from the local structure around the cerium ions, determined by extended X-ray absorption fine structure (EXAFS) measurements in the solid state. The composition of all Ce–O clusters was confirmed by elemental analysis, NMR and IR spectroscopy. The Ce–O clusters are highly soluble, up to 101 and 136 g/L for 1-Cl and 2-Cl, respectively, in organic solvents, which strongly depends on the type of cluster and functionalization of the benzoate ligands. Moreover, the structural and compositional integrity of dissolved clusters in different solvents was established. Recrystallization of 1-Cl from dichloromethane (DCM) and Raman spectroscopy confirm the integrity of both cluster types in solution. Further examination by EXAFS measurements on the Ce K-edge of clusters containing 4-chlorobenzoate reveals that only minor changes in the cerium environment of 1-Cl are observed upon dissolution in THF, DCM, and dioxane, while the results for 2-Cl indicate a partial degradation upon dissolution. After proving the stability, a cluster solution of 1-Cl was used to impregnate the mesoporous metal–organic framework Cr-MIL-101. Extensive characterization by PXRD, inductively coupled plasma-optical emission spectroscopy, and energy-dispersive X-ray spectroscopy, as well as thermogravimetry and N2-sorption measurements, confirm the successful insertion of Ce–O clusters into the large mesoporous cages of the framework. Due to the combination of high surface area and potential catalytic activity, the Cluster@MOF materials could be of high interest for application in heterogeneous catalysis

Solubility and Stability of Hexanuclear Ce(IV)–O Clusters

Stable molecular clusters are of interest for targeted deposition in porous materials. In this work, we report the discovery of two new molecular Ce–O clusters of composition [Ce6O4(OH)4(NO3)4(DMF)4(C7H4O2X)8]·(DMF)4(H2O)2 (1-X) and [Ce6O4(OH)4(H2O)6(NO3)6(C7H4O2X)6] (2-X) (X = −Cl, −CHO, and −Br). Both cluster types contain a similar hexanuclear building unit, and crystal structures were determined from single-crystal X-ray diffraction or 3D electron diffraction data and subsequent Rietveld refinements against powder X-ray diffraction (PXRD) data. The crystal structure data is complemented by results from the local structure around the cerium ions, determined by extended X-ray absorption fine structure (EXAFS) measurements in the solid state. The composition of all Ce–O clusters was confirmed by elemental analysis, NMR and IR spectroscopy. The Ce–O clusters are highly soluble, up to 101 and 136 g/L for 1-Cl and 2-Cl, respectively, in organic solvents, which strongly depends on the type of cluster and functionalization of the benzoate ligands. Moreover, the structural and compositional integrity of dissolved clusters in different solvents was established. Recrystallization of 1-Cl from dichloromethane (DCM) and Raman spectroscopy confirm the integrity of both cluster types in solution. Further examination by EXAFS measurements on the Ce K-edge of clusters containing 4-chlorobenzoate reveals that only minor changes in the cerium environment of 1-Cl are observed upon dissolution in THF, DCM, and dioxane, while the results for 2-Cl indicate a partial degradation upon dissolution. After proving the stability, a cluster solution of 1-Cl was used to impregnate the mesoporous metal–organic framework Cr-MIL-101. Extensive characterization by PXRD, inductively coupled plasma-optical emission spectroscopy, and energy-dispersive X-ray spectroscopy, as well as thermogravimetry and N2-sorption measurements, confirm the successful insertion of Ce–O clusters into the large mesoporous cages of the framework. Due to the combination of high surface area and potential catalytic activity, the Cluster@MOF materials could be of high interest for application in heterogeneous catalysis

Solubility and Stability of Hexanuclear Ce(IV)–O Clusters

Stable molecular clusters are of interest for targeted deposition in porous materials. In this work, we report the discovery of two new molecular Ce–O clusters of composition [Ce6O4(OH)4(NO3)4(DMF)4(C7H4O2X)8]·(DMF)4(H2O)2 (1-X) and [Ce6O4(OH)4(H2O)6(NO3)6(C7H4O2X)6] (2-X) (X = −Cl, −CHO, and −Br). Both cluster types contain a similar hexanuclear building unit, and crystal structures were determined from single-crystal X-ray diffraction or 3D electron diffraction data and subsequent Rietveld refinements against powder X-ray diffraction (PXRD) data. The crystal structure data is complemented by results from the local structure around the cerium ions, determined by extended X-ray absorption fine structure (EXAFS) measurements in the solid state. The composition of all Ce–O clusters was confirmed by elemental analysis, NMR and IR spectroscopy. The Ce–O clusters are highly soluble, up to 101 and 136 g/L for 1-Cl and 2-Cl, respectively, in organic solvents, which strongly depends on the type of cluster and functionalization of the benzoate ligands. Moreover, the structural and compositional integrity of dissolved clusters in different solvents was established. Recrystallization of 1-Cl from dichloromethane (DCM) and Raman spectroscopy confirm the integrity of both cluster types in solution. Further examination by EXAFS measurements on the Ce K-edge of clusters containing 4-chlorobenzoate reveals that only minor changes in the cerium environment of 1-Cl are observed upon dissolution in THF, DCM, and dioxane, while the results for 2-Cl indicate a partial degradation upon dissolution. After proving the stability, a cluster solution of 1-Cl was used to impregnate the mesoporous metal–organic framework Cr-MIL-101. Extensive characterization by PXRD, inductively coupled plasma-optical emission spectroscopy, and energy-dispersive X-ray spectroscopy, as well as thermogravimetry and N2-sorption measurements, confirm the successful insertion of Ce–O clusters into the large mesoporous cages of the framework. Due to the combination of high surface area and potential catalytic activity, the Cluster@MOF materials could be of high interest for application in heterogeneous catalysis

Solubility and Stability of Hexanuclear Ce(IV)–O Clusters

Stable molecular clusters are of interest for targeted deposition in porous materials. In this work, we report the discovery of two new molecular Ce–O clusters of composition [Ce6O4(OH)4(NO3)4(DMF)4(C7H4O2X)8]·(DMF)4(H2O)2 (1-X) and [Ce6O4(OH)4(H2O)6(NO3)6(C7H4O2X)6] (2-X) (X = −Cl, −CHO, and −Br). Both cluster types contain a similar hexanuclear building unit, and crystal structures were determined from single-crystal X-ray diffraction or 3D electron diffraction data and subsequent Rietveld refinements against powder X-ray diffraction (PXRD) data. The crystal structure data is complemented by results from the local structure around the cerium ions, determined by extended X-ray absorption fine structure (EXAFS) measurements in the solid state. The composition of all Ce–O clusters was confirmed by elemental analysis, NMR and IR spectroscopy. The Ce–O clusters are highly soluble, up to 101 and 136 g/L for 1-Cl and 2-Cl, respectively, in organic solvents, which strongly depends on the type of cluster and functionalization of the benzoate ligands. Moreover, the structural and compositional integrity of dissolved clusters in different solvents was established. Recrystallization of 1-Cl from dichloromethane (DCM) and Raman spectroscopy confirm the integrity of both cluster types in solution. Further examination by EXAFS measurements on the Ce K-edge of clusters containing 4-chlorobenzoate reveals that only minor changes in the cerium environment of 1-Cl are observed upon dissolution in THF, DCM, and dioxane, while the results for 2-Cl indicate a partial degradation upon dissolution. After proving the stability, a cluster solution of 1-Cl was used to impregnate the mesoporous metal–organic framework Cr-MIL-101. Extensive characterization by PXRD, inductively coupled plasma-optical emission spectroscopy, and energy-dispersive X-ray spectroscopy, as well as thermogravimetry and N2-sorption measurements, confirm the successful insertion of Ce–O clusters into the large mesoporous cages of the framework. Due to the combination of high surface area and potential catalytic activity, the Cluster@MOF materials could be of high interest for application in heterogeneous catalysis

Solubility and Stability of Hexanuclear Ce(IV)–O Clusters

Stable molecular clusters are of interest for targeted deposition in porous materials. In this work, we report the discovery of two new molecular Ce–O clusters of composition [Ce6O4(OH)4(NO3)4(DMF)4(C7H4O2X)8]·(DMF)4(H2O)2 (1-X) and [Ce6O4(OH)4(H2O)6(NO3)6(C7H4O2X)6] (2-X) (X = −Cl, −CHO, and −Br). Both cluster types contain a similar hexanuclear building unit, and crystal structures were determined from single-crystal X-ray diffraction or 3D electron diffraction data and subsequent Rietveld refinements against powder X-ray diffraction (PXRD) data. The crystal structure data is complemented by results from the local structure around the cerium ions, determined by extended X-ray absorption fine structure (EXAFS) measurements in the solid state. The composition of all Ce–O clusters was confirmed by elemental analysis, NMR and IR spectroscopy. The Ce–O clusters are highly soluble, up to 101 and 136 g/L for 1-Cl and 2-Cl, respectively, in organic solvents, which strongly depends on the type of cluster and functionalization of the benzoate ligands. Moreover, the structural and compositional integrity of dissolved clusters in different solvents was established. Recrystallization of 1-Cl from dichloromethane (DCM) and Raman spectroscopy confirm the integrity of both cluster types in solution. Further examination by EXAFS measurements on the Ce K-edge of clusters containing 4-chlorobenzoate reveals that only minor changes in the cerium environment of 1-Cl are observed upon dissolution in THF, DCM, and dioxane, while the results for 2-Cl indicate a partial degradation upon dissolution. After proving the stability, a cluster solution of 1-Cl was used to impregnate the mesoporous metal–organic framework Cr-MIL-101. Extensive characterization by PXRD, inductively coupled plasma-optical emission spectroscopy, and energy-dispersive X-ray spectroscopy, as well as thermogravimetry and N2-sorption measurements, confirm the successful insertion of Ce–O clusters into the large mesoporous cages of the framework. Due to the combination of high surface area and potential catalytic activity, the Cluster@MOF materials could be of high interest for application in heterogeneous catalysis

Co-Ligand Dependent Formation and Phase Transformation of Four Porphyrin-Based Cerium Metal–Organic Frameworks

The four porphyrin-based metal–organic frameworks (MOFs) containing Ce³⁺ ions, [Ce₄(H₂TCPP)₃­(DMF)₂­(H₂O)₄] (<b>CAU-18</b>), [Ce₄­(H₂TCPP)₃]­·22H₂O (<b>CAU-18a</b>), [Ce₃(H₂TCPP)₂­(BA-X)­(HBA-X/H₂O)₂]­·2HBA-X­·<i>n</i>H₂O (<b>CAU-19-X</b> with X = H, 2Cl, 3Cl, 4Cl, 3CO₂H, 4NH₂, 4NO₂, HBA = C₇H₄O₂), and [Ce₂(H₂TCPP)­(C₇H₄O₂NO₂)₂]­·2DMF (<b>Ce-PMOF-4NO₂</b>) were synthesized using the linker 4-tetracarboxyphenylporphyrin (H₆TCPP). The formation of the respective MOFs depends mainly on the presence of a coligand in the synthesis mixture. <b>CAU-18</b> was obtained in the absence of a coligand, while <b>CAU-19-X</b> was observed when the benzoic acid derivative HBA-X (X = H, 2Cl, 3Cl, 4Cl, 3CO₂H, 4NH₂) was added. In the case that HBA-4NO₂ was used as a coligand, yet another compound <b>Ce-PMOF-4NO₂</b> is obtained. The structures of <b>CAU-18</b> and <b>CAU-19-H</b> were determined from single crystal X-ray diffraction data, while the structure of <b>Ce-PMOF-4NO₂</b> was refined from powder X-ray diffraction data by the Rietveld method. Activation of <b>CAU-18</b> and <b>Ce-PMOF-4NO₂</b> resulted in phase transformations. Thermal treatment of <b>CAU-18</b> at 250 °C leads to <b>CAU-18a</b>, which is porous toward N₂ and H₂O, while treatment of <b>Ce-PMOF-4NO₂</b> in organic solvents at 70 °C leads to the formation of <b>CAU-19</b>-<b>4NO</b>_<b>2</b>, which cannot be synthesized directly. All <b>CAU-19-X</b> compounds are porous toward N₂ and H₂O, and the specific surface areas vary between 330 and 600 m² g^–1 depending on the size of the incorporated coligand. <b>CAU-18</b>, <b>CAU-18a</b>, and <b>CAU-19-X</b> are thermally stable in air up to 330 °C and chemically stable in H₂O and all tested organic solvents. Ce L₃-edge X-ray absorption near edge structure measurements revealed that exclusively Ce³⁺ ions are present in the title compounds, despite the use of (NH₄)₂­[Ce­(NO₃)₆] in all syntheses. In addition, the crystallization of <b>CAU-18</b> and <b>CAU-19-H</b> was investigated in situ by synchrotron powder X-ray diffraction at DESY, Hamburg, using reaction temperatures between 110 and 130 °C. The data were evaluated using the approach by Gualtieri to determine the probability of nucleation (<i>P</i>_n) and the Arrhenius activation energy for nucleation (<i>k</i>_n) and crystal growth (<i>k</i>_g). The Arrhenius activation energies for the nucleation were determined as 47(2) and 56(3) kJ mol^–1 and for crystal growth 45(4) and 58(5) kJ mol^–1 for <b>CAU-18</b> and <b>CAU-19-H</b>, respectively. The induction time (<i>t</i>_ind), in which no crystalline products are detected, and the total reaction time to achieve full conversion (<i>t</i>_com) are shortened at higher temperatures. Furthermore, the maximum of the probability of nucleation is shifted to earlier reaction times with increasing temperature

Temperature- and Pressure-Dependent Hydrogen Concentration in Supported PdH_<i>x</i> Nanoparticles by Pd K‑Edge X‑ray Absorption Spectroscopy

Hydride formation in palladium nanoparticles was studied by Pd K-edge X-ray absorption spectroscopy in both the near-edge (XANES) and the extended (EXAFS) regions and by X-ray diffraction (XRD) both <i>in situ</i> as a function of temperature and hydrogen pressure. In contrast to EXAFS and XRD, which probe Pd–Pd interatomic distance changes, the direct effect of hydrogen concentration on the electronic palladium structure is observed in the intensities and the peak positions in the XANES region. By using theoretical simulations, we propose a simple analysis of hydrogen concentration based on the changes of relative peak amplitudes in the XANES region, which correlate with interatomic distance changes determined by both EXAFS and XRD. By the quantitative analysis of XANES difference spectra, we have developed a scheme to determine the hydrogen concentration in palladium nanoparticles without applying any additional calibration procedures with alternative experimental techniques

Probing Reactive Platinum Sites in UiO-67 Zirconium Metal–Organic Frameworks

We present three methods of the synthesis of zirconium metal–organic framework UiO-67 functionalized with platinum bipyridine coordination complexes (bpydcPt^IICl₂ and bpydcPt^IVCl₄) acting as linkers in the MOF framework. These Pt complexes can be reduced to bpydcPt⁰ under flow of H₂ gas in the 600–700 K range, as probed by a sophisticated parametric refinement of in situ EXAFS data. IR spectroscopy testifies the high coordinative unsaturation of the reduced centers, able to form bpydcPt⁰(CO)₂ dicarbonyl complexes upon CO adsorption. The large pore size of UiO-67 allows for ligand exchange between 2 Cl^– and even bulky ligands such as toluene-3,4-dithiol. Framework bpydcPt^IICl₂ complexes can also be oxidized at room temperature to bpydcPt^IVBr₄ through oxidative addition of liquid Br₂. XANES spectroscopy was used to monitor the changes in the Pt oxidation state along the observed reactions. Platinum bipyridine-functionalized UiO-67-Pt displays the same exceptional stability as the parent material as testified on both long and local range by in situ XRPD and Pt L₃-edge EXAFS data