I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[30461]
Open Access
Abstract: Hydrogen-bonded organic frameworks (HOFs) with low densities and high porosities are rare and challenging to design because most molecules have a strong energetic preference for close packing. Crystal structure prediction (CSP) can rank the crystal packings available to an organic molecule based on their relative lattice energies. This has become a powerful tool for the a priori design of porous molecular crystals. Previously, we combined CSP with structure-property predictions to generate energy–structure–function (ESF) maps for a series of triptycene-based molecules with quinoxaline groups. From these ESF maps, triptycene trisquinoxalinedione (TH5) was predicted to form a previously unknown low-energy HOF (TH5-A) with a remarkably low density of 0.374 g cm-3 and three-dimensional (3-D) pores. Here, we demonstrate the reliability of those ESF maps by discovering this TH5-A polymorph experimentally. This material has a high accessible surface area of 3,284 m2 g-1, as measured by nitrogen adsorption, making it one of the most porous HOFs reported to date.
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Apr 2023
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I11-High Resolution Powder Diffraction
I19-Small Molecule Single Crystal Diffraction
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Donglin
He
,
Chengxi
Zhao
,
Linjiang
Chen
,
Marc
Little
,
Samantha
Chong
,
Rob
Clowes
,
Katherine
Mckie
,
Mark
Roper
,
Graeme
Day
,
Ming
Liu
,
Andrew
Cooper
Diamond Proposal Number(s):
[21726, 17193]
Abstract: Ethyl acetate is an important chemical raw material and solvent. It is also a key volatile organic compound in the brewing industry and a marker for lung cancer. Materials that are highly selective toward ethyl acetate are needed for its separation and detection. Here, we report a trianglimine macrocycle ( TAMC ) that selectively adsorbs ethyl acetate by forming a solvate. Crystal structure prediction showed this to be the lowest energy solvate structure available. This solvate leaves a metastable, ‘templated’ cavity after solvent removal. Adsorption and breakthrough experiments confirmed that imprinted TAMC has adequate adsorption kinetics to separate ethyl acetate from azeotropic mixtures with ethanol, which is a challenging and energy‐intensive industrial separation.
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Apr 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]
Abstract: Three-dimensional (3D) covalent organic frameworks (COFs) are rare because there is a limited choice of organic building blocks that offer multiple reactive sites in a polyhedral geometry. Here, we synthesized an organic cage molecule (cage-6-NH2), which was used as a triangular prism node to yield the first cage-based 3D COF, 3D-CageCOF-1. This COF adopts an unreported twofold interpenetrated acs topology and exhibits reversible dynamic behavior, switching between a small-pore (sp) structure and a large-pore (lp) structure. It also shows high CO2 uptake and captures water at low humidity (<40%). This demonstrates the potential for expanding the structural complexity of 3D COFs by using organic cages as the building units.
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Sep 2020
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I19-Small Molecule Single Crystal Diffraction
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Catherine M.
Aitchison
,
Christopher M.
Kane
,
David P.
Mcmahon
,
Peter R.
Spackman
,
Angeles
Pulido
,
Xiaoyan
Wang
,
Liam
Wilbraham
,
Linjiang
Chen
,
Rob
Clowes
,
Martijn A.
Zwijnenburg
,
Reiner Sebastian
Sprick
,
Marc A.
Little
,
Graeme M.
Day
,
Andrew I.
Cooper
Diamond Proposal Number(s):
[21726]
Open Access
Abstract: We show that a hydrogen-bonded framework, TBAP-α, with extended π-stacked pyrene columns has a sacrificial photocatalytic hydrogen production rate of up to 3108 μmol g−1 h−1. This is the highest activity reported for a molecular organic crystal. By comparison, a chemically-identical but amorphous sample of TBAP was 20–200 times less active, depending on the reaction conditions, showing unambiguously that crystal packing in molecular crystals can dictate photocatalytic activity. Crystal structure prediction (CSP) was used to predict the solid-state structure of TBAP and other functionalised, conformationally-flexible pyrene derivatives. Specifically, we show that energy–structure–function (ESF) maps can be used to identify molecules such as TBAP that are likely to form extended π-stacked columns in the solid state. This opens up a methodology for the a priori computational design of molecular organic photocatalysts and other energy-relevant materials, such as organic electronics.
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Apr 2020
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[9282]
Abstract: A porous organic cage crystal, α-CC2, shows unexpected adsorption of sulphur hexafluoride (SF6) in its cage cavities, which are formally occluded even to the smallest diatomic gas, H2, according to a pore analysis of the static crystal structure. In situ powder X-ray diffraction (PXRD) experiments provide unequivocal evidence for the presence of (SF6) inside the ‘occluded’ cage voids, pointing to a mechanism of dynamic flexibility of the system. By combining PXRD results with molecular dynamics simulations, we build a molecular level picture of the cooperative porosity in α-CC2 that facilitates the passage of (SF6) into the cage voids.
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Mar 2020
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I11-High Resolution Powder Diffraction
I19-Small Molecule Single Crystal Diffraction
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Ming
Liu
,
Linda
Zhang
,
Marc A.
Little
,
Venkat
Kapil
,
Michele
Ceriotti
,
Siyuan
Yang
,
Lifeng
Ding
,
Daniel L.
Holden
,
Rafael
Balderas-Xicohténcatl
,
Donglin
He
,
Rob
Clowes
,
Samantha Y.
Chong
,
Gisela
Schütz
,
Linjiang
Chen
,
Michael
Hirscher
,
Andrew I.
Cooper
Diamond Proposal Number(s):
[21726, 17193]
Abstract: The separation of hydrogen isotopes for applications such as nuclear fusion is a major challenge. Current technologies are energy intensive and inefficient. Nanoporous materials have the potential to separate hydrogen isotopes by kinetic quantum sieving, but high separation selectivity tends to correlate with low adsorption capacity, which can prohibit process scale-up. In this study, we use organic synthesis to modify the internal cavities of cage molecules to produce hybrid materials that are excellent quantum sieves. By combining small-pore and large-pore cages together in a single solid, we produce a material with optimal separation performance that combines an excellent deuterium/hydrogen selectivity (8.0) with a high deuterium uptake (4.7 millimoles per gram).
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Oct 2019
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I11-High Resolution Powder Diffraction
I19-Small Molecule Single Crystal Diffraction
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Xiaoyan
Wang
,
Linjiang
Chen
,
Samantha Y.
Chong
,
Marc A.
Little
,
Yongzhen
Wu
,
Wei-Hong
Zhu
,
Rob
Clowes
,
Yong
Yan
,
Martijn A.
Zwijnenburg
,
Reiner Sebastian
Sprick
,
Andrew I.
Cooper
Diamond Proposal Number(s):
[15777, 17193]
Abstract: Nature uses organic molecules for light harvesting and photosynthesis, but most man-made water splitting catalysts are inorganic semiconductors. Organic photocatalysts, while attractive because of their synthetic tunability, tend to have low quantum efficiencies for water splitting. Here we present a crystalline covalent organic framework (COF) based on a benzo-bis(benzothiophene sulfone) moiety that shows a much higher activity for photochemical hydrogen evolution than its amorphous or semicrystalline counterparts. The COF is stable under long-term visible irradiation and shows steady photochemical hydrogen evolution with a sacrificial electron donor for at least 50 hours. We attribute the high quantum efficiency of fused-sulfone-COF to its crystallinity, its strong visible light absorption, and its wettable, hydrophilic 3.2 nm mesopores. These pores allow the framework to be dye-sensitized, leading to a further 61% enhancement in the hydrogen evolution rate up to 16.3 mmol g−1 h−1. The COF also retained its photocatalytic activity when cast as a thin film onto a support.
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Oct 2018
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[12336]
Open Access
Abstract: The first examples of core–shell porous molecular crystals are described. The physical properties of the core–shell crystals, such as surface hydrophobicity, CO2 /CH4 selectivity, are controlled by the chemical composition of the shell. This shows that porous core–shell molecular crystals can exhibit synergistic properties that out‐perform materials built from the individual, constituent molecules.
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Jun 2018
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I11-High Resolution Powder Diffraction
I19-Small Molecule Single Crystal Diffraction
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Anna G.
Slater
,
Paul S.
Reiss
,
Angeles
Pulido
,
Marc A.
Little
,
Daniel L.
Holden
,
Linjiang
Chen
,
Samantha Y.
Chong
,
Ben M.
Alston
,
Rob
Clowes
,
Maciej
Haranczyk
,
Michael E.
Briggs
,
Tom
Hasell
,
Graeme M.
Day
,
Andrew I.
Cooper
Diamond Proposal Number(s):
[11231, 12336]
Open Access
Abstract: The physical properties of 3-D porous solids are defined by their molecular geometry. Hence, precise control of pore size, pore shape, and pore connectivity are needed to tailor them for specific applications. However, for porous molecular crystals, the modification of pore size by adding pore-blocking groups can also affect crystal packing in an unpredictable way. This precludes strategies adopted for isoreticular metal–organic frameworks, where addition of a small group, such as a methyl group, does not affect the basic framework topology. Here, we narrow the pore size of a cage molecule, CC3, in a systematic way by introducing methyl groups into the cage windows. Computational crystal structure prediction was used to anticipate the packing preferences of two homochiral methylated cages, CC14-R and CC15-R, and to assess the structure–energy landscape of a CC15-R/CC3-S cocrystal, designed such that both component cages could be directed to pack with a 3-D, interconnected pore structure. The experimental gas sorption properties of these three cage systems agree well with physical properties predicted by computational energy–structure–function maps.
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Jun 2017
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I11-High Resolution Powder Diffraction
I19-Small Molecule Single Crystal Diffraction
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Angeles
Pulido
,
Linjiang
Chen
,
Tomasz
Kaczorowski
,
Daniel
Holden
,
Marc A.
Little
,
Samantha Y.
Chong
,
Benjamin J.
Slater
,
David P.
Mcmahon
,
Baltasar
Bonillo
,
Chloe J.
Stackhouse
,
Andrew
Stephenson
,
Christopher M.
Kane
,
Rob
Clowes
,
Tom
Hasell
,
Andrew I.
Cooper
,
Graeme M.
Day
Diamond Proposal Number(s):
[8728, 12336]
Abstract: Molecular crystals cannot be designed in the same manner as macroscopic objects, because they do not assemble according to simple, intuitive rules. Their structures result from the balance of many weak interactions, rather than from the strong and predictable bonding patterns found in metal–organic frameworks and covalent organic frameworks. Hence, design strategies that assume a topology or other structural blueprint will often fail. Here we combine computational crystal structure prediction and property prediction to build energy–structure–function maps that describe the possible structures and properties that are available to a candidate molecule. Using these maps, we identify a highly porous solid, which has the lowest density reported for a molecular crystal so far. Both the structure of the crystal and its physical properties, such as methane storage capacity and guest-molecule selectivity, are predicted using the molecular structure as the only input. More generally, energy–structure–function maps could be used to guide the experimental discovery of materials with any target function that can be calculated from predicted crystal structures, such as electronic structure or mechanical properties.
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Mar 2017
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