Single-crystal XRD and solid-state NMR structural resolution of a layered fluorinated gallium phosphate: RbGa 3 (PO 4 ) 2 (HPO 4 )F 4 ·C 5 N 2 H 16 ·2H 2 O (MIL-145)

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Spektroskopické a teoretické studium supramolekulárních komplexů symetrických porfyrinů s chirálními guesty

Certain types of porphyrins can be used as achiral agent for determination of enantiomeric excess (ee) of chiral molecules. Particular organic chiral molecule (guest) and porphyrin (host) form host-guest complex while inducing nonequiv- alency of particular proton resonances in symmetrical host. It causes splitting of NMR signals linearly dependent on ee of guest. In this work we investigated com- plexation of di-brombenzylated oxoporphyrin with chiral camphorsulfonic acid. NMR titration revealed that they form complex with 1:1 stoichiometry with as- sociation constant K ≈ 5 × 104 l/mol. We confirmed linear dependence of split- ting of host β-protons on ee of guest. Low temperature measurements revealed two conformations of host-guest complex with population around 0.7:0.3 (at −60 ◦ C). DFT quantum mechanical computations at BLYP/3-21G* level revealed also two conformations with population 0.79:0.21. NMR shifts were computed on this geometries with method GIAO/PBE1PBE/6-31G(2df,2pd) and compared to experimental values.

High-Resolution Structural Characterization of Two Layered Aluminophosphates by Synchrotron Powder Diffraction and NMR Crystallographies

The syntheses and structure resolution process of two highly complex powdered aluminophosphates with an original 5:7 Al/P ratio are presented: [Al₅(OH)­(PO₄)₃(PO₃OH)₄] [NH₃(CH₂)₂NH₃]₂ [2H₂O], compound <b>1</b>, and [Al₅(PO₄)₅(PO₃OH)₂] [NH₃(CH₂)₃NH₃]₂ [H₂O], compound <b>2</b>. We have previously reported the structure of the periodic part of <b>1</b> by coupling synchrotron powder diffraction and solid-state nuclear magnetic resonance (NMR) crystallographies. With a similar strategy, that is, input of large parts of the building blocks determined by analysis of the ²⁷Al–³¹P correlation pattern of the two-dimensional (2D) NMR spectrum in the structure search process, we first determine the periodic structure of <b>2</b>, using the powder synchrotron diffraction data as cost function. Both <b>1</b> and <b>2</b> are layered materials, in which the inorganic layers contain five P and seven Al inequivalent atoms, with aluminum atoms that are found in three different coordination states, AlO₄, AlO₅, and AlO₆, and the interlayer space contains the amines and water molecules. In <b>1</b>, the inorganic layers are stacked on each other with a 4₂ element of symmetry along the <i>c</i>-axis, while they are stacked with a 180° rotation angle in <b>2</b>. By analysis of a set of high-resolution 1D and 2D NMR spectra (³¹P, ²⁷Al, ¹H, ¹⁵N, ¹³C, ²⁷Al–³¹P, ¹H–³¹P, and ¹H–¹⁴N), the structure analysis of <b>1</b> and <b>2</b> is extended beyond the strict periodicity, to which diffraction is restricted, and provides localization of the hydroxyl groups and water molecules in the frameworks and an attempt to correlate the presence of these latter species to the structural features of the two samples is presented. Finally, the dehydration/rehydration processes occurring in these solids are analyzed. The methodology of the structure determination for these dehydrated forms uses the same principles, combining X-ray powder diffraction and solid-state NMR data

High-Resolution Structural Characterization of Two Layered Aluminophosphates by Synchrotron Powder Diffraction and NMR Crystallographies

The syntheses and structure resolution process of two highly complex powdered aluminophosphates with an original 5:7 Al/P ratio are presented: [Al₅(OH)­(PO₄)₃(PO₃OH)₄] [NH₃(CH₂)₂NH₃]₂ [2H₂O], compound <b>1</b>, and [Al₅(PO₄)₅(PO₃OH)₂] [NH₃(CH₂)₃NH₃]₂ [H₂O], compound <b>2</b>. We have previously reported the structure of the periodic part of <b>1</b> by coupling synchrotron powder diffraction and solid-state nuclear magnetic resonance (NMR) crystallographies. With a similar strategy, that is, input of large parts of the building blocks determined by analysis of the ²⁷Al–³¹P correlation pattern of the two-dimensional (2D) NMR spectrum in the structure search process, we first determine the periodic structure of <b>2</b>, using the powder synchrotron diffraction data as cost function. Both <b>1</b> and <b>2</b> are layered materials, in which the inorganic layers contain five P and seven Al inequivalent atoms, with aluminum atoms that are found in three different coordination states, AlO₄, AlO₅, and AlO₆, and the interlayer space contains the amines and water molecules. In <b>1</b>, the inorganic layers are stacked on each other with a 4₂ element of symmetry along the <i>c</i>-axis, while they are stacked with a 180° rotation angle in <b>2</b>. By analysis of a set of high-resolution 1D and 2D NMR spectra (³¹P, ²⁷Al, ¹H, ¹⁵N, ¹³C, ²⁷Al–³¹P, ¹H–³¹P, and ¹H–¹⁴N), the structure analysis of <b>1</b> and <b>2</b> is extended beyond the strict periodicity, to which diffraction is restricted, and provides localization of the hydroxyl groups and water molecules in the frameworks and an attempt to correlate the presence of these latter species to the structural features of the two samples is presented. Finally, the dehydration/rehydration processes occurring in these solids are analyzed. The methodology of the structure determination for these dehydrated forms uses the same principles, combining X-ray powder diffraction and solid-state NMR data

High-Resolution Structural Characterization of Two Layered Aluminophosphates by Synchrotron Powder Diffraction and NMR Crystallographies

The syntheses and structure resolution process of two highly complex powdered aluminophosphates with an original 5:7 Al/P ratio are presented: [Al₅(OH)­(PO₄)₃(PO₃OH)₄] [NH₃(CH₂)₂NH₃]₂ [2H₂O], compound <b>1</b>, and [Al₅(PO₄)₅(PO₃OH)₂] [NH₃(CH₂)₃NH₃]₂ [H₂O], compound <b>2</b>. We have previously reported the structure of the periodic part of <b>1</b> by coupling synchrotron powder diffraction and solid-state nuclear magnetic resonance (NMR) crystallographies. With a similar strategy, that is, input of large parts of the building blocks determined by analysis of the ²⁷Al–³¹P correlation pattern of the two-dimensional (2D) NMR spectrum in the structure search process, we first determine the periodic structure of <b>2</b>, using the powder synchrotron diffraction data as cost function. Both <b>1</b> and <b>2</b> are layered materials, in which the inorganic layers contain five P and seven Al inequivalent atoms, with aluminum atoms that are found in three different coordination states, AlO₄, AlO₅, and AlO₆, and the interlayer space contains the amines and water molecules. In <b>1</b>, the inorganic layers are stacked on each other with a 4₂ element of symmetry along the <i>c</i>-axis, while they are stacked with a 180° rotation angle in <b>2</b>. By analysis of a set of high-resolution 1D and 2D NMR spectra (³¹P, ²⁷Al, ¹H, ¹⁵N, ¹³C, ²⁷Al–³¹P, ¹H–³¹P, and ¹H–¹⁴N), the structure analysis of <b>1</b> and <b>2</b> is extended beyond the strict periodicity, to which diffraction is restricted, and provides localization of the hydroxyl groups and water molecules in the frameworks and an attempt to correlate the presence of these latter species to the structural features of the two samples is presented. Finally, the dehydration/rehydration processes occurring in these solids are analyzed. The methodology of the structure determination for these dehydrated forms uses the same principles, combining X-ray powder diffraction and solid-state NMR data

CO2 Hydrogenation over Pt-Containing UiO-67 Zr-MOFs—The Base Case

CO2 hydrogenation was carried out over Pt-containing UiO-67 Zr-MOFs at T = 220–280 °C and ambient pressure, with H2/CO2 = 0.2–9 and contact times, τ = 0.004–0.01 gcat×min×ml−1. The catalysts were characterized by XRD, N2 adsorption, FESEM, TEM and HRTEM, dissolution-NMR, CO chemisorption, IR spectroscopy and TGA. A positive correlation was observed between the degree of Pt reduction and CO2 conversion. Contact time variation experiments showed that CO is a primary product of reaction, while CH4 is a secondary product. Testing of catalyst crystals with 0.15 and 2.0 micron crystal size, respectively, revealed no influence of diffusion on the reaction rate. Comparison to a conventional Pt/SiO2 catalyst showed very similar activation energy, with Eapp = 50±3 kJ×mol−1. However, the turn-over frequency over Pt/SiO2 was significantly lower, and Pt/SiO2 did not yield methane as product. The Pt-containing UiO-67 Zr-MOF catalyst showed stable activity during 60 hours testing

CO2 Hydrogenation over Pt-Containing UiO-67 Zr-MOFs—The Base Case

CO2 hydrogenation was carried out over Pt-containing UiO-67 Zr-MOFs at T = 220–280 °C and ambient pressure, with H2/CO2 = 0.2–9 and contact times, τ = 0.004–0.01 gcat×min×ml−1. The catalysts were characterized by XRD, N2 adsorption, FESEM, TEM and HRTEM, dissolution-NMR, CO chemisorption, IR spectroscopy and TGA. A positive correlation was observed between the degree of Pt reduction and CO2 conversion. Contact time variation experiments showed that CO is a primary product of reaction, while CH4 is a secondary product. Testing of catalyst crystals with 0.15 and 2.0 micron crystal size, respectively, revealed no influence of diffusion on the reaction rate. Comparison to a conventional Pt/SiO2 catalyst showed very similar activation energy, with Eapp = 50±3 kJ×mol−1. However, the turn-over frequency over Pt/SiO2 was significantly lower, and Pt/SiO2 did not yield methane as product. The Pt-containing UiO-67 Zr-MOF catalyst showed stable activity during 60 hours testing