I07-Surface & interface diffraction
I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[24359, 23666]
Open Access
Abstract: Membranes with high selectivity offer an attractive route to molecular separations, where technologies such as distillation and chromatography are energy intensive. However, it remains challenging to fine tune the structure and porosity in membranes, particularly to separate molecules of similar size. Here, we report a process for producing composite membranes that comprise crystalline porous organic cage films fabricated by interfacial synthesis on a polyacrylonitrile support. These membranes exhibit ultrafast solvent permeance and high rejection of organic dyes with molecular weights over 600 g mol−1. The crystalline cage film is dynamic, and its pore aperture can be switched in methanol to generate larger pores that provide increased methanol permeance and higher molecular weight cut-offs (1,400 g mol−1). By varying the water/methanol ratio, the film can be switched between two phases that have different selectivities, such that a single, ‘smart’ crystalline membrane can perform graded molecular sieving. We exemplify this by separating three organic dyes in a single-stage, single-membrane process.
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Jan 2022
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I15-1-X-ray Pair Distribution Function (XPDF)
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Diamond Proposal Number(s):
[18630]
Open Access
Abstract: The structures of Zr and Hf metal–organic frameworks (MOFs) are very sensitive to small changes in synthetic conditions. One key difference affecting the structure of UiO MOF phases is the shape and nuclearity of Zr or Hf metal clusters acting as nodes in the framework; although these clusters are crucial, their evolution during MOF synthesis is not fully understood. In this paper, we explore the nature of Hf metal clusters that form in different reaction solutions, including in a mixture of DMF, formic acid, and water. We show that the choice of solvent and reaction temperature in UiO MOF syntheses determines the cluster identity and hence the MOF structure. Using in situ X-ray pair distribution function measurements, we demonstrate that the evolution of different Hf cluster species can be tracked during UiO MOF synthesis, from solution stages to the full crystalline framework, and use our understanding to propose a formation mechanism for the hcp UiO-66(Hf) MOF, in which first the metal clusters aggregate from the M6 cluster (as in fcu UiO-66) to the hcp-characteristic M12 double cluster and, following this, the crystalline hcp framework forms. These insights pave the way toward rationally designing syntheses of as-yet unknown MOF structures, via tuning the synthesis conditions to select different cluster species.
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Nov 2021
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B18-Core EXAFS
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Diamond Proposal Number(s):
[25651]
Open Access
Abstract: In this paper, we demonstrate a novel synthetic route to assemble reduced graphene oxide (rGO) uniformly coated on BiSI composite and investigate its potential as the active electrode material for supercapacitors. In this strategy, graphene oxide (GO) was not a simple physical mixture with the BiSI material but bismuth cations were uniformly anchored on the surface of GO by chemical bonding during material growth and the size of GO can determine the final size of rGO coated BiSI composite. The galvanostatic charge–discharge measurement results show that the BiSI–rGO electrode has a maximum specific capacity of 234 C g−1 at the current density of 1 A g−1 and excellent capacity retention of 92.4% after 2000 cycles. In situ XANES and EXAFS were employed to study the electrochemical oxidation and reduction processes of the bismuth-based material with rGO coating and investigate the origins of the structural stabilities. The results show that our novel rGO coating route can not only significantly increase the capacity but also improve cycling stability.
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Jun 2021
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I11-High Resolution Powder Diffraction
I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[21726, 23666]
Open Access
Abstract: A molecular crystal of a 2-D hydrogen-bonded organic framework (HOF) undergoes an unusual structural transformation after solvent removal from the crystal pores during activation. The conformationally flexible host molecule, ABTPA, adapts its molecular conformation during activation to initiate a framework expansion. The microcrystalline activated phase was characterized by three-dimensional electron diffraction (3D ED), which revealed that ABTPA uses out-of-plane anthracene units as adaptive structural anchors. These units change orientation to generate an expanded, lower density framework material in the activated structure. The porous HOF, ABTPA-2, has robust dynamic porosity (SABET = 1183 m2 g-1) and exhibits negative area thermal expansion. We use crystal structure prediction (CSP) to understand the underlying energetics behind the structural transformation and discuss the challenges facing CSP for such flexible molecules.
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Jun 2020
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I02-Macromolecular Crystallography
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Wei
Wang
,
Jill M.
Marinis
,
Allison M.
Beal
,
Shivraj
Savadkar
,
Yue
Wu
,
Mohammed
Khan
,
Pardeep S.
Taunk
,
Nan
Wu
,
Wenyu
Su
,
Jingjing
Wu
,
Aarif
Ahsan
,
Emma
Kurz
,
Ting
Chen
,
Inedouye
Yaboh
,
Fei
Li
,
Johana
Gutierrez
,
Brian
Diskin
,
Mautin
Hundeyin
,
Michael
Reilly
,
John D.
Lich
,
Philip A.
Harris
,
Mukesh K.
Mahajan
,
James H.
Thorpe
,
Pamela
Nassau
,
Julie E.
Mosley
,
Joshua
Leinwand
,
Juan A.
Kochen Rossi
,
Ankita
Mishra
,
Berk
Aykut
,
Michael
Glacken
,
Atsuo
Ochi
,
Narendra
Verma
,
Jacqueline I.
Kim
,
Varshini
Vasudevaraja
,
Dennis
Adeegbe
,
Christina
Almonte
,
Ece
Bagdatlioglu
,
Deirdre J.
Cohen
,
Kwok-Kin
Wong
,
John
Bertin
,
George
Miller
Abstract: Pancreatic ductal adenocarcinoma (PDA) is characterized by immune tolerance and immunotherapeutic resistance. We discovered upregulation of receptor-interacting serine/threonine protein kinase 1 (RIP1) in tumor-associated macrophages (TAMs) in PDA. To study its role in oncogenic progression, we developed a selective small-molecule RIP1 inhibitor with high in vivo exposure. Targeting RIP1 reprogrammed TAMs toward an MHCIIhiTNFα+IFNγ+ immunogenic phenotype in a STAT1-dependent manner. RIP1 inhibition in TAMs resulted in cytotoxic T cell activation and T helper cell differentiation toward a mixed Th1/Th17 phenotype, leading to tumor immunity in mice and in organotypic models of human PDA. Targeting RIP1 synergized with PD1-and inducible co-stimulator-based immunotherapies. Tumor-promoting effects of RIP1 were independent of its co-association with RIP3. Collectively, our work describes RIP1 as a checkpoint kinase governing tumor immunity.
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Nov 2018
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I12-JEEP: Joint Engineering, Environmental and Processing
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Hamish
Yeung
,
Adam F.
Sapnik
,
Felicity
Massingberd-Mundy
,
Michael W.
Gaultois
,
Yue
Wu
,
Duncan X.
Fraser
,
Sebastian
Henke
,
Roman
Pallach
,
Niclas
Heidenreich
,
Oxana
Magdysyuk
,
Nghia T.
Vo
,
Andrew L.
Goodwin
Diamond Proposal Number(s):
[16354, 16450]
Abstract: There is an increasingly large amount of interest in metal‐organic frameworks (MOFs) for a variety of applications, from gas sensing and separations to electronics and catalysis. Their exciting properties arise from their modular architectures, which self‐assemble from different combinations of metal‐based and organic building units. However, the exact mechanisms by which they crystallize remain poorly understood, thus limiting any realisation of real “structure by design”. We report important new insight into MOF formation, gained using in situ X‐ray diffraction, pH and turbidity measurements to uncover for the first time the evolution of metastable intermediate species in the canonical zeolitic imidazolate framework system, ZIF‐8. We reveal that the intermediate species exist in a dynamic pre‐equilibrium prior to network assembly and, depending on the reactant concentrations and the progress of reaction, the pre‐equilibrium can be made to favour under‐ or over‐coordinated Zn‐imidazolate species, thus accelerating or inhibiting crystallization, respectively. We thereby find that concentration can be effectively used as a synthetic handle to directly control particle size, with great implications for industrial scale‐up and gas sorption applications. These finding enables us to rationalise the apparent contradictions between previous studies of ZIF‐8 and, importantly, opens up new opportunities for the control of crystallization in network solids more generally, from the design of local structure to assembly of particles with precise dimensions.
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Nov 2018
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I15-Extreme Conditions
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Diamond Proposal Number(s):
[13843]
Abstract: Crystallization via metastable phases plays an important role in chemical manufacturing, bio-mineralization, and protein crystallization, but the kinetic pathways leading from metastable phases to the stable crystalline modifications are not well understood. In particular, the fast crys-tallization of amorphous intermediates makes a detailed characterization challenging. To circum-vent this problem, we devised a system that allows trapping and stabilizing the amorphous in-termediates of representative carbonates (calcium, strontium, barium, manganese, and cadmium). The long-term stabilization of these transient species enabled a detailed investigation of their composition, structure, and morphology. Total scattering experiments with high-energy syn-chrotron radiation revealed a short-range order of several Ångström in all amorphous intermedi-ates. From the synchrotron data, a structural model of amorphous calcium carbonate was de-rived that indicates a lower coordination number of calcium compared to the crystalline poly-morphs. Our study shows that a multi-step crystallization pathway via amorphous intermediates is open to many carbonates. We could isolate and characterize these transient species, thereby providing new insights into their crystallization mechanism.
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Oct 2018
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I15-Extreme Conditions
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Diamond Proposal Number(s):
[13843]
Abstract: Amorphous calcium carbonate (ACC) is an important precursor in the biomineralization of crystal-line CaCO3. The lifetime of transient ACC in nature is regulated by an organic matrix, in order to use it as an intermediate storage buffer or as a permanent structural element. The relevance of ACC in material science is related to our understanding of CaCO3 crystallization pathways. ACC can be obtained by liquid-liquid phase separation, and it is typically stabilized with of the help of macro-molecules. We have prepared ACC by milling calcite in a planetary ball mill. The ball-milled amor-phous calcium carbonate (BM-ACC) was stabilized with small amounts of Na2CO3. The addition of foreign ions in form of Na2CO3 is crucial to achieve complete amorphization. Their incorporation generates defects that hinder recrystallization kinetically. In contrast to wet-chemically prepared ACC, the solvent-free approach makes BM-ACC an anhydrous modification. The amorphization process was monitored by quantitative Fourier transform infrared (FTIR) spectroscopy and solid state 23Na magic angle spinning nuclear magnetic resonance (23Na MAS-NMR) spectroscopy, which is highly sensitive to changes in the symmetry of the local sodium environment. The struc-ture of BM-ACC was probed by vibrational spectroscopy (FTIR, Raman) and solid state MAS NMR (23Na, 13C) spectroscopy. A structural model revealing the partly unsaturated coordination sphere for the Ca2+ ions was derived from the analysis of total scattering data with high-energy synchrotron radiation. Our findings aid in the understanding of mechanochemical amorphization of calcium carbonate and emphasize the effect of impurities on the stabilization of the amorphous phase, which allowed the synthesis of a so far unknown defect variant of ACC with new proper-ties. This may also represent a general approach to obtain new amorphous phases in a variety of different systems.
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Aug 2018
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I15-Extreme Conditions
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Diamond Proposal Number(s):
[12370]
Open Access
Abstract: We investigate the pressure-dependent mechanical behaviour of the zeolitic imidazolate framework ZIF-4 (M(im)2; M2+ = Co2+ or Zn2+, im− = imidazolate) with high pressure, synchrotron powder X-ray diffraction and mercury intrusion measurements. A displacive phase transition from a highly compressible open pore (op) phase with continuous porosity (space group Pbca, bulk modulus ∼1.4 GPa) to a closed pore (cp) phase with inaccessible porosity (space group P21/c, bulk modulus ∼3.3–4.9 GPa) is triggered by the application of mechanical pressure. Over the course of the transitions, both ZIF-4 materials contract by about 20% in volume. However, the threshold pressure, the reversibility and the immediate repeatability of the phase transition depend on the metal cation. ZIF-4(Zn) undergoes the op–cp phase transition at a hydrostatic mechanical pressure of only 28 MPa, while ZIF-4(Co) requires about 50 MPa to initiate the transition. Interestingly, ZIF-4(Co) fully returns to the op phase after decompression, whereas ZIF-4(Zn) remains in the cp phase after pressure release and requires subsequent heating to switch back to the op phase. These variations in high pressure behaviour can be rationalised on the basis of the different electron configurations of the respective M2+ ions (3d10 for Zn2+ and 3d7 for Co2+). Our results present the first examples of op–cp phase transitions (i.e. breathing transitions) of ZIFs driven by mechanical pressure and suggest potential applications of these functional materials as shock absorbers, nanodampers, or in mechanocalorics.
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Jan 2018
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I19-Small Molecule Single Crystal Diffraction
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Shijing
Sun
,
Zeyu
Deng
,
Yue
Wu
,
Fengxia
Wei
,
Furkan
Halis Isikgor
,
Federico
Brivio
,
Michael W.
Gaultois
,
Jianyong
Ouyang
,
Paul D.
Bristowe
,
Anthony K.
Cheetham
,
Gregor
Kieslich
Diamond Proposal Number(s):
[14165]
Abstract: We investigate the variable temperature (100–450 K) and high-pressure (p = ambient − 0.74 GPa) crystal chemistry of the black perovskite formamidinium lead iodide, [(NH2)2CH]PbI3, using single crystal X-ray diffraction. In both cases we find a phase transition to a tetragonal phase. Our experimental results are combined with first principles calculations, providing information about the electronic properties of [(NH2)2CH]PbI3 as well as the most probable orientation of the [(NH2)2CH]+ cations.
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Jun 2017
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