I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[8833]
Abstract: A novel open-framework germanate, |NC2H8∥N2C6H18|[Ge7O14.5F2]·4H2O denoted SU-65 (SU = Stockholm University), with 24-ring channels and a very low framework density of 8.9 Ge atoms per 1000 Å3 was synthesized under hydro-solvothermal conditions. The framework of SU-65 is built of 5-connected Ge7 clusters decorating the fee net and is a framework orientation isomer to ASU-16. Half of the 8- and 12-rings in ASU-16 are instead 10-rings in SU-65 due to the different orientations of half of the clusters in the crystal structure. Flexibility of the frameworks is also influenced by the orientation of the clusters. The unique unit cell angle in SU-65 changes upon heating, unlike ASU-16 which only undergoes changes in unit cell lengths. SU-65 undergoes significant structural changes at 180 °C in a vacuum, forming SU-65ht. The crystal structure of SU-65ht was investigated by rotation electron diffraction, X-ray powder diffraction, and infrared spectroscopy. Through these techniques it was deduced that SU-65ht has similar clusters, symmetry, and topology as SU-65, but one of the unit cell lengths is shortened by approximately 5 Å. This corresponds to a 22% decrease in unit cell volume.
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Dec 2016
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[10379]
Abstract: A bismuth-based metal–organic framework (MOF), [Bi(BTC)(H2O)]·2H2O·MeOH denoted CAU-17, was synthesized and found to have an exceptionally complicated structure with helical Bi–O rods cross-linked by 1,3,5-benzenetricarboxylate (BTC3–) ligands. Five crystallographically independent 1D channels including two hexagonal channels, two rectangular channels, and one triangular channel have accessible diameters of 9.6, 9.6, 3.6, 3.6, and 3.4 Å, respectively. The structure is further complicated by twinning. Rod-incorporated MOF structures typically have underlying nets with only one unique node and three or four unique edges. In contrast, topological analysis of CAU-17 revealed unprecedented complexity for a MOF structure with 54 unique nodes and 135 edges. The complexity originates from the rod packing and the rods themselves, which are related to aperiodic helices.
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Jan 2016
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I11-High Resolution Powder Diffraction
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Qingxia
Yao
,
Antonio
Bermejo Gómez
,
Jie
Su
,
Vlad
Pascanu
,
Yifeng
Yun
,
Haoquan
Zheng
,
Hong
Chen
,
Leifeng
Liu
,
Hani Nasser
Abdelhamid
,
Belén
Martín-Matute
,
Xiaodong
Zou
Abstract: A series of highly porous isoreticular lanthanide-based metal–organic frameworks (LnMOFs) denoted as SUMOF-7I to SUMOF-7IV (SU = Stockholm University; Ln = La, Ce, Pr, Nd, Sm, Eu, and Gd) have been synthesized using tritopic carboxylates as the organic linkers. The SUMOF-7 materials display one-dimensional pseudohexagonal channels with the pore diameter gradually enlarged from 8.4 to 23.9 Å, as a result of increasing sizes of the organic linkers. The structures have been solved by single crystal X-ray diffraction or rotation electron diffraction (RED) combined with powder X-ray diffraction (PXRD). The SUMOF-7 materials exhibit robust architectures with permanent porosity. More importantly, they exhibit exceptionally high thermal and chemical stability. We show that, by inclusion of organic dye molecules, the luminescence properties of the MOFs can be elaborated and modulated, leading to promising applications in sensing and optics.
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Jul 2015
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B18-Core EXAFS
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Diamond Proposal Number(s):
[12120]
Abstract: The chemical stability of metal–organic frameworks (MOFs) is a major factor preventing their use in industrial processes. Herein, it is shown that judicious choice of the base for the Suzuki–Miyaura cross-coupling reaction can
avoid decomposition of the MOF catalyst Pd@MIL-101-NH2 (Cr). Four bases were compared for the reaction: K2CO3, KF, Cs2CO3 and CsF. The carbonates were the most active
and achieved excellent yields in shorter reaction times than the fluorides. However, powder XRD and N2 sorption measurements showed that the MOF catalyst was degraded when carbonates were used but remained crystalline and
porous with the fluorides. XANES measurements revealed that the trimeric chromium cluster of Pd@MIL-101-NH2 (Cr) is still present in the degraded MOF. In addition, the different
countercations of the base significantly affected the catalytic activity of the material. TEM revealed that after several catalytic runs many of the Pd nanoparticles (NPs) had migrated
to the external surface of the MOF particles and formed larger aggregates. The Pd NPs were larger after catalysis with caesium bases compared to potassium bases.
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Jul 2015
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I19-Small Molecule Single Crystal Diffraction
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Abstract: In this study, we report the formation of a new crystal structure, ZIF-CO3-1, which results from the reaction of Zn2+, 2-methylimidazole, and carbonate. ZIF-CO3-1 can be synthesized solvothermally in N,N-dimethylformamide (DMF)/water (H2O) or by utilizing of CO2 gas at various temperatures in DMF/H2O or H2O. This reaction selectively consumes CO2 because CO2 is incorporated in the ZIF as carbonate. CO2 can be quantitatively released by acidifying the ZIF. Powder X-ray diffraction, single-crystal X-ray diffraction, FTIR spectroscopy, scanning electron microscopy, elemental analysis, and thermogravimetric analysis were used to characterize the ZIF structure. ZIF-CO3-1 (chemical formula C9H(10)N4O(3)Zn(2)), crystallizes in the orthorhombic crystal system with noncentrosymmetric space group Pba2.
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Feb 2015
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I19-Small Molecule Single Crystal Diffraction
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Abstract: Open-framework structures, such as inorganic oxides and coordination polymers,
have been extensively studied for their ability to selectively accommodate guest
species in their pores and channels. Such materials have applications in
heterogeneous catalysis, sorption, separation, and ion exchange. Many of these
phases however do not form sufficiently large crystals for structure
X-ray powder diffraction (XPD) is also complicated by the severe overlap problem
introduced by the typically large unit cell lengths. We have shown that complicated
framework structures with can be solved using direct-space methods if the
secondary building units have been identified, even when using low resolution XPD
data. In more complex cases charge-flipping can be used in combination with
parallel tempering.
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Nov 2014
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I15-Extreme Conditions
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Diamond Proposal Number(s):
[5052]
Abstract: Throughout much of condensed matter science, correlated disorder is a key to material function. While structural and compositional defects are known to exist within a variety of metal–organic frameworks (MOFs), the prevailing understanding is that these defects are only ever included in a random manner. Here we show—using a combination of diffuse scattering, electron microscopy, anomalous X-ray scattering and pair distribution function measurements—that correlations between defects can in fact be introduced and controlled within a hafnium terephthalate MOF. The nanoscale defect structures that emerge are an analogue of correlated Schottky vacancies in rocksalt-structured transition metal monoxides and have implications for storage, transport, optical and mechanical responses. Our results suggest how the diffraction behaviour of some MOFs might be reinterpreted, and establish a strategy of exploiting correlated nanoscale disorder as a targetable and desirable motif in MOF design.
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Jun 2014
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I11-High Resolution Powder Diffraction
I19-Small Molecule Single Crystal Diffraction
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Abstract: An open-framework germanate denoted as SU-79 with the chemical formula [Ge12.5O26(OH)2][Ni(C3N2H10)2]1.1(NH4)0.8(C3N2H12)0.5(C3N2H10)1.5(H2O)2 has been synthesized under hydro/solvothermal conditions using [Ni(1,2-pda)2]2+ (1,2-pda = 1,2-diaminopropane) and 1,2-pda as templates. Owing to the complicated pseudo-merohedral twinning in the crystals, the rotation electron diffraction (RED) method was used for the unit cell and space group determination. The structure of SU-79 was solved and refined based on synchrotron single crystal X-ray diffraction data. SU-79 exhibits a 3D open germanate framework built with Ge13 clusters, consisting of a 3D channel system with interconnected 10- and 11-ring channels. Interestingly, helical GeO4 tetrahedral chains with left-handed/right-handed chirality were found in the structure. The [Ni(1,2-pda)2]2+ complexes, adopting in a square-planar geometry, show a structure directing role on the SU-79 framework via hydrogen bonds. Comparing with its related structure, SU-67, the formation of the pseudo-merohedric twinning in SU-79 was also discussed
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Mar 2014
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[8833]
Abstract: Three three-dimensional (3D) open-framework vanadoborates, denoted as SUT-6-Zn, SUT-6-Mn, and SUT-6-Ni, were synthesized using diethylenetriamine as a template. SUT-6-Zn, SUT-6-Mn, and SUT-6-Ni are isostructural and built from (VO)12O6 B18O36(OH)6 clusters bridged by ZnO5, MnO6, and NiO6 polyhedra, respectively, to form the 3D frameworks. SUT-6 is the first vanadoborate with a 3D framework. The framework follows a semiregular hxg net topology with a 2-fold interpenetrated diamond-like channel system. The amount of template used in the synthesis played an important role in the dimensionality of the resulting vanadoborate structures. A small amount of diethylenetriamine led to the formation of this first 3D vanadoborate framework, while an increased amount of diethylenetriamine resulted in vanadoborates with zero-dimensional (0D) and one-dimensional (1D) structures. SUT-6-Zn was proved to be an efficient heterogeneous precatalyst for the oxidation of alkylbenzenes.
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Dec 2013
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I11-High Resolution Powder Diffraction
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Abstract: Two families of metal–organic frameworks (MOFs), MIL-88 and MIL-101 built by trinuclear transition metal (TM) clusters (TM = Cr, Fe, or Sc), have been known for several years, but their syntheses are often reported separately. In fact, these MOFs are polymorphs, or framework isomers: they are assembled from the same metal secondary building units and organic linkers, but the connectivity of these components differs. Here we report for the first time the synthesis of the vanadium MOF MIL-88B(V) and compare its synthesis parameters to those of MIL-47(V) and the recently reported MIL-101(V). The properties of MIL-88B(V) and MIL-101(V) are remarkably different. MIL-88B(V) can “breathe” and is responsive to different solvents, while MIL-101(V) is rigid and contains mesoporous cages. MIL-101(V) exhibits the highest specific surface area among vanadium MOFs discovered so far. In addition, both MIL-88B(V) and MIL-101(V) transform to MIL-47 at higher temperatures. We have also identified the key synthesis parameters that control the formation of MIL-88B(V), MIL-101(V), and MIL-47: temperature, time, and pH. This relates to the rate of reaction between the metal and linkers, which has been monitored by ex situ X-ray powder diffraction and V K-edge X-ray absorption spectroscopy during MOF synthesis. It is therefore important to fully study the synthesis conditions to improve our understanding of framework isomerism in MOFs.
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Oct 2013
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