I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[31578, 36629]
Open Access
Abstract: The separation of carbon dioxide from industrial flue gas streams using porous materials is often thwarted by humidity. Most porous sorbents adsorb water more effectively than CO2. Hence, water can out-compete CO2 for adsorption sites, lowering the working CO2 sorption capacity and increasing sorbent regeneration costs. Here, two pyrene-based hydrogen bonded organic frameworks (HOFs) are described that can separate CO2 under humid conditions. The framework building blocks were chosen in a high-throughput density functional theory screen, followed by crystal structure prediction (CSP) to target a hydrophobic two-dimensionally porous framework. Gas sorption experiments showed selective adsorption of CO2 and exceptionally low water adsorption in these HOFs. Dynamic column breakthrough measurements using mixed gas environments showed that the CO2 working capacity was totally unaffected by water under simulated flue gas conditions up to 75% relative humidity. One of the CO2-selective HOFs, diMeTBAP-α, was shown by CSP to be the most thermodynamically stable structure on the crystal energy landscape. This stability prediction was reflected by experiments, where an isostructural, scalable analogue of diMeTBAP-α, MeTBAP-α, retained its porosity and crystallinity after boiling in aqueous acids, which is important for carbon capture from acidic, humid flue gas.
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Jun 2025
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I19-Small Molecule Single Crystal Diffraction
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Open Access
Abstract: Metal–organic frameworks (MOFs) are useful synthetic materials that are built by the programmed assembly of metal nodes and organic linkers. The success of MOFs results from the isoreticular principle, which allows families of structurally analogous frameworks to be built in a predictable way. This relies on directional coordinate covalent bonding to define the framework geometry. However, isoreticular strategies do not translate to other common crystalline solids, such as organic salts, in which the intermolecular ionic bonding is less directional. Here we show that chemical knowledge can be combined with computational crystal-structure prediction6 (CSP) to design porous organic ammonium halide salts that contain no metals. The nodes in these salt frameworks are tightly packed ionic clusters that direct the materials to crystallize in specific ways, as demonstrated by the presence of well-defined spikes of low-energy, low-density isoreticular structures on the predicted lattice energy landscapes. These energy landscapes allow us to select combinations of cations and anions that will form thermodynamically stable, porous salt frameworks with channel sizes, functionalities and geometries that can be predicted a priori. Some of these porous salts adsorb molecular guests such as iodine in quantities that exceed those of most MOFs, and this could be useful for applications such as radio-iodine capture. More generally, the synthesis of these salts is scalable, involving simple acid–base neutralization, and the strategy makes it possible to create a family of non-metal organic frameworks that combine high ionic charge density with permanent porosity.
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May 2024
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[30461]
Open Access
Abstract: Here we report a two-step, hierarchical synthesis that assembles a trigonal prismatic organic cage into a more symmetric, higher-order tetrahedral cage, or ‘cage of cages’. Both the preformed [2+3] trigonal prismatic cage building blocks and the resultant tetrahedral [4[2+3]+6]cage molecule are constructed using ether bridges. This strategy affords the [4[2+3]+6]cage molecule excellent hydrolytic stability that is not a feature of more common dynamic cage linkers, such as imines. Despite its relatively high molar mass (3,001 g mol−1), [4[2+3]+6]cage exhibits good solubility and crystallizes into a porous superstructure with a surface area of 1,056 m2 g−1. By contrast, the [2+3] building block is not porous. The [4[2+3]+6]cage molecule shows high CO2 and SF6 uptakes due to its polar skeleton. The preference for the [4[2+3]+6]cage molecule over other cage products can be predicted by computational modelling, as can its porous crystal packing, suggesting a broader design strategy for the hierarchical assembly of organic cages with synthetically engineered functions.
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Apr 2024
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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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I19-Small Molecule Single Crystal Diffraction
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Haofan
Yang
,
Chao
Li
,
Tao
Liu
,
Thomas
Fellowes
,
Samantha Y.
Chong
,
Luca
Catalano
,
Mounib
Bahri
,
Weiwei
Zhang
,
Yongjie
Xu
,
Lunjie
Liu
,
Wei
Zhao
,
Adrian M.
Gardner
,
Rob
Clowes
,
Nigel D.
Browning
,
Xiaobo
Li
,
Alexander J.
Cowan
,
Andrew I.
Cooper
Abstract: Molecular packing controls optoelectronic properties in organic molecular nanomaterials. Here we report a donor–acceptor organic molecule (2,6-bis(4-cyanophenyl)-4-(9-phenyl-9H-carbazol-3-yl)pyridine-3,5-dicarbonitrile) that exhibits two aggregate states in aqueous dispersions: amorphous nanospheres and ordered nanofibres with π–π molecular stacking. The nanofibres promote sacrificial photocatalytic H2 production (31.85 mmol g−1 h−1) while the nanospheres produce hydrogen peroxide (H2O2) (3.20 mmol g−1 h−1 in the presence of O2). This is the first example of an organic photocatalyst that can be directed to produce these two different solar fuels simply by changing the molecular packing. These different packings affect energy band levels, the extent of excited state delocalization, the excited state dynamics, charge transfer to O2 and the light absorption profile. We use a combination of structural and photophysical measurements to understand how this influences photocatalytic selectivity. This illustrates the potential to achieve multiple photocatalytic functionalities with a single organic molecule by engineering nanomorphology and solid-state packing.
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Jan 2023
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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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I11-High Resolution Powder Diffraction
I19-Small Molecule Single Crystal Diffraction
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Guo-Hong
Ning
,
Peng
Cui
,
Igor V.
Sazanovich
,
James T.
Pegg
,
Qiang
Zhu
,
Zhongfu
Pang
,
Rong-Jia
Wei
,
Mike
Towrie
,
Kim E.
Jelfs
,
Marc A.
Little
,
Andrew I.
Cooper
Diamond Proposal Number(s):
[21726, 17193]
Abstract: Host-guest complexation is an important supramolecular route to materials. Clear design rules have been developed for complexation in solution. This has proved more challenging for solid-state host-guest co-crystals because they often exhibit polymorphism, leading many researchers to focus instead on bonded frameworks, such as metal-organic frameworks. Here, we report an anthracene-based organic cage (1) that forms isoskeletal host-guest co-crystals with five similarly sized solid organic guests. The co-crystals were designed using inexpensive computational methods to identify appropriate guests that have packing coefficients (PCs) ranging from 44% to 50%, coupled with consideration of the guest shape. By complexing highly emissive BODIPY guests into the host structure, we enhanced its two-photon excited photoluminescent properties by a factor of six. Our crystal design approach was also transferrable to hard-to-design ternary organic crystals that were accessed by inserting specific guests into different sized voids in the host.
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Oct 2021
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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]
Open Access
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):
[15777, 17193]
Abstract: The discovery of new structural and functional materials is driven by phase identification, often using X-ray diffraction (XRD). Automation has accelerated the rate of XRD measurements, greatly outpacing XRD analysis techniques that remain manual, time-consuming, error-prone and impossible to scale. With the advent of autonomous robotic scientists or self-driving laboratories, contemporary techniques prohibit the integration of XRD. Here, we describe a computer program for the autonomous characterization of XRD data, driven by artificial intelligence (AI), for the discovery of new materials. Starting from structural databases, we train an ensemble model using a physically accurate synthetic dataset, which outputs probabilistic classifications—rather than absolutes—to overcome the overconfidence in traditional neural networks. This AI agent behaves as a companion to the researcher, improving accuracy and offering substantial time savings. It is demonstrated on a diverse set of organic and inorganic materials characterization challenges. This method is directly applicable to inverse design approaches and robotic discovery systems, and can be immediately considered for other forms of characterization such as spectroscopy and the pair distribution function.
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Apr 2021
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B21-High Throughput SAXS
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Daniel
Mcdowall
,
Benjamin J.
Greeves
,
Rob
Clowes
,
Kate
Mcaulay
,
Ana M.
Fuentes‐caparrós
,
Lisa
Thomson
,
Nikul
Khunti
,
Nathan
Cowieson
,
Michael C.
Nolan
,
Matthew
Wallace
,
Andrew I.
Cooper
,
Emily R.
Draper
,
Alexander J.
Cowan
,
Dave J.
Adams
Diamond Proposal Number(s):
[20362]
Open Access
Abstract: Amino acid functionalized perylene bisimides (PBIs) form self‐assembled structures in solution, the nature of which depends on the local environment. Using a high‐throughput photocatalysis setup, five PBIs are studied for the hydrogen evolution reaction (HER) under a range of conditions (pH and hole scavenger concentration) across 350 experiments to explore the relationship between supramolecular structure and photocatalytic activity. Using small angle X‐ray scattering (SAXS), NMR spectroscopy and ultraviolet‐visible (UV‐vis) absorption spectroscopy, it is shown that photocatalytic activity is determined by the nature of the self‐assembled aggregate that is formed, demonstrating the potential of self‐assembly to tune activity. There is a clear correlation between the presence of charged flexible cylindrical aggregates and the occurrence of photocatalytic H2 production, with UV–vis spectroscopy indicating that the most active structure type has a distinctive form of π‐aggregation which is proposed to enable efficient charge separation across multiple PBI units.
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Oct 2020
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