I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[17193]
Open Access
Abstract: We demonstrate two renewable crosslinkers that can stabilise sustainable high sulfur content polymers, via inverse-vulcanisation. With increasing levels of sulfur produced as a waste byproduct from hydrodesulfurisation of crude oil and gas, the need to find a method to utilise this abundant feedstock is pressing. The resulting sulfur copolymers can be synthesised relatively quickly, using a one-pot solvent free method, producing polymeric materials that are shape-persistent solids at room temperature and compare well to other inverse vulcanised polymers. The physical properties of these high sulfur polymeric materials, coupled with the ability to produce them sustainably, allow broad potential utility.
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Aug 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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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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Diamond Proposal Number(s):
[12336, 11231]
Abstract: The control of solid state assembly for porous organic cages is more challenging than for extended frameworks, such as metal–organic frameworks. Chiral recognition is one approach to achieving this control. Here we investigate chiral analogues of cages that were previously studied as racemates. We show that chiral cages can be produced directly from chiral precursors or by separating racemic cages by co-crystallisation with a second chiral cage, opening up a route to producing chiral cages from achiral precursors. These chiral cages can be cocrystallized in a modular, ‘isoreticular’ fashion, thus modifying porosity, although some chiral pairings require a specific solvent to direct the crystal into the desired packing mode. Certain cages are shown to interconvert chirality in solution, and the steric factors governing this behavior are explored both by experiment and by computational modelling.
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May 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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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[11231]
Abstract: By synthesizing derivatives of a trans-1,2-diaminocyclohexane precursor, three new functionalized porous organic cages were prepared with different chemical functionalities on the cage periphery. The introduction of twelve methyl groups (CC16) resulted in frustration of the cage packing mode, which more than doubled the surface area compared to the parent cage, CC3. The analogous installation of twelve hydroxyl groups provided an imine cage (CC17) that combines permanent porosity with the potential for post-synthetic modification of the cage exterior. Finally, the incorporation of bulky dihydroethanoanthracene groups was found to direct self-assembly towards the formation of a larger [8+12] cage, rather than the expected [4+6], cage molecule (CC18). However, CC18 was found to be non-porous, most likely due to cage collapse upon desolvation.
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Nov 2016
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I11-High Resolution Powder Diffraction
I19-Small Molecule Single Crystal Diffraction
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A. G.
Slater
,
M. A.
Little
,
A.
Pulido
,
S. Y.
Chong
,
D.
Holden
,
L.
Chen
,
C.
Morgan
,
X.
Wu
,
G.
Cheng
,
R.
Clowes
,
M. E.
Briggs
,
T.
Hasell
,
K. E.
Jelfs
,
G. M.
Day
,
A. I.
Cooper
Diamond Proposal Number(s):
[8728, 11231, 12336]
Abstract: Synthetic control over pore size and pore connectivity is the crowning achievement for porous metal–organic frameworks (MOFs). The same level of control has not been achieved for molecular crystals, which are not defined by strong, directional intermolecular coordination bonds. Hence, molecular crystallization is inherently less controllable than framework crystallization, and there are fewer examples of ‘reticular synthesis’, in which multiple building blocks can be assembled according to a common assembly motif. Here we apply a chiral recognition strategy to a new family of tubular covalent cages to create both 1D porous nanotubes and 3D diamondoid pillared porous networks. The diamondoid networks are analogous to MOFs prepared from tetrahedral metal nodes and linear ditopic organic linkers. The crystal structures can be rationalized by computational lattice-energy searches, which provide an in silico screening method to evaluate candidate molecular building blocks. These results are a blueprint for applying the ‘node and strut’ principles of reticular synthesis to molecular crystals.
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Nov 2016
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I19-Small Molecule Single Crystal Diffraction
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Ming
Liu
,
Linjiang
Chen
,
Scott
Lewis
,
Samantha Y.
Chong
,
Marc A.
Little
,
Tom
Hasell
,
Iain M.
Aldous
,
Craig M.
Brown
,
Martin W.
Smith
,
Carole A.
Morrison
,
Laurence
Hardwick
,
Andrew I.
Cooper
Diamond Proposal Number(s):
[8728]
Open Access
Abstract: Proton conduction is a fundamental process in biology and in devices such as proton exchange membrane fuel cells. To maximize proton conduction, three-dimensional conduction pathways are preferred over one-dimensional pathways, which prevent conduction in two dimensions. Many crystalline porous solids to date show one-dimensional proton conduction. Here we report porous molecular cages with proton conductivities (up to 10−3 S cm−1 at high relative humidity) that compete with extended metal-organic frameworks. The structure of the organic cage imposes a conduction pathway that is necessarily three-dimensional. The cage molecules also promote proton transfer by confining the water molecules while being sufficiently flexible to allow hydrogen bond reorganization. The proton conduction is explained at the molecular level through a combination of proton conductivity measurements, crystallography, molecular simulations and quasi-elastic neutron scattering. These results provide a starting point for high-temperature, anhydrous proton conductors through inclusion of guests other than water in the cage pores.
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Sep 2016
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[9282]
Open Access
Abstract: The practical adsorption properties of molecular porous solids can be dominated by dynamic flexibility but these effects are still poorly understood. Here, we combine molecular simulations and experiments to rationalize the adsorption behavior of a flexible porous organic cage.
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Apr 2016
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I11-High Resolution Powder Diffraction
I19-Small Molecule Single Crystal Diffraction
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Tom
Hasell
,
Marcin
Miklitz
,
Andrew
Stephenson
,
Marc
Little
,
Sam
Chong
,
Rob
Clowes
,
Linjiang
Chen
,
Daniel
Holden
,
Gareth A.
Tribello
,
Kim E.
Jelfs
,
Andrew I.
Cooper
Diamond Proposal Number(s):
[8728, 9282]
Open Access
Abstract: A series of porous organic cages is examined for the selective adsorption of sulphur hexafluoride (SF6) over nitrogen. Despite lacking any metal sites, a porous cage, CC3, shows the highest SF6/N2 selectivity reported for any material at ambient temperature and pressure, which translates to real separations in a gas breakthrough column. The SF6 uptake of these materials is considerably higher than would be expected from the static pore structures. The location of SF6 within these materials is elucidated by x-ray crystallography, and it is shown that cooperative diffusion and structural rearrangements in these molecular crystals can rationalize their superior SF6/N2 selectivity.
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Jan 2016
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