161 results found
Tan R, Wang A, Ye C, et al., 2023, Thin film composite membranes with regulated crossover and water migration for long-life aqueous redox flow batteries., Advanced Science, Vol: 10, Pages: 1-11, ISSN: 2198-3844
Redox flow batteries (RFBs) are promising for large-scale long-duration energy storage owing to their inherent safety, decoupled power and energy, high efficiency, and longevity. Membranes constitute an important component that affects mass transport processes in RFBs, including ion transport, redox-species crossover, and the net volumetric transfer of supporting electrolytes. Hydrophilic microporous polymers, such as polymers of intrinsic microporosity (PIM), are demonstrated as next-generation ion-selective membranes in RFBs. However, the crossover of redox species and water migration through membranes are remaining challenges for battery longevity. Here, a facile strategy is reported for regulating mass transport and enhancing battery cycling stability by employing thin film composite (TFC) membranes prepared from a PIM polymer with optimized selective-layer thickness. Integration of these PIM-based TFC membranes with a variety of redox chemistries allows for the screening of suitable RFB systems that display high compatibility between membrane and redox couples, affording long-life operation with minimal capacity fade. Thickness optimization of TFC membranes further improves cycling performance and significantly restricts water transfer in selected RFB systems.
Wolpert EH, Tarzia A, Jelfs KE, 2023, The effect of disorder in multi-component covalent organic frameworks, Chemical Communications, Vol: 59, Pages: 6909-6912, ISSN: 1359-7345
We examined the effect of two different types of linker distribution---random or correlated distribution---on the pore size and shape within single-layers of three multi-component COFs. We reveal a relationship between linker distribution and the porosity of COF solid solutions. The methods presented in this paper are generalisable and could be used in further studies to examine the properties of disordered framework materials.
Kearsey RJ, Tarzia A, Little MA, et al., 2023, Competitive aminal formation during the synthesis of a highly soluble, isopropyl-decorated imine porous organic cage., Chemical Communications, Vol: 59, Pages: 3731-3734, ISSN: 1359-7345
The synthesis of a new porous organic cage decorated with isopropyl moieties (CC21) was achieved from the reaction of triformylbenzene and an isopropyl functionalised diamine. Unlike structurally analogous porous organic cages, its synthesis proved challenging due to competitive aminal formation, rationalised using control experiments and computational modelling. The use of an additional amine was found to increase conversion to the desired cage.
Wang A, Tan R, Liu D, et al., 2023, Ion-selective microporous polymer membranes with hydrogen-bond and salt-bridge networks for aqueous organic redox flow batteries, Advanced Materials, Vol: 35, Pages: 1-12, ISSN: 0935-9648
Redox flow batteries (RFBs) have great potential for long-duration grid-scale energy storage. Ion conducting membranes are a crucial component in RFBs, allowing charge-carrying ions to transport while preventing the cross-mixing of redox couples. Commercial Nafion membranes are widely used in RFBs, but their unsatisfactory ionic and molecular selectivity as well as high costs limit the performance and the widespread deployment of this technology. To extend the longevity and reduce the cost of RFB systems, inexpensive ion-selective membranes are highly desired that concurrently deliver low ionic resistance and high selectivity towards redox-active species. In this work, high-performance RFB membranes are fabricated from blends of carboxylate- and amidoxime-functionalized polymers of intrinsic microporosity (PIMs) that exploit the beneficial properties of both polymers. The enthalpy-driven formation of cohesive interchain interactions, including hydrogen bonds and salt bridges, facilitates the microscopic miscibility of the blends, while ionizable functional groups within the sub-nanometer pores allow optimization of membrane ion transport functions. The resulting microporous membranes demonstrate fast cation conduction with low crossover of redox-active molecular species, enabling improved power ratings and reduced capacity fade in aqueous RFBs using anthraquinone and ferrocyanide as redox couples. This article is protected by copyright. All rights reserved.
Davies JA, Tarzia A, Ronson TK, et al., 2023, Tetramine Aspect Ratio and Flexibility Determine Framework Symmetry for Zn<sub>8</sub>L<sub>6</sub> Self‐Assembled Structures, Angewandte Chemie, Vol: 135, ISSN: 0044-8249
<jats:title>Abstract</jats:title><jats:p>We derive design principles for the assembly of rectangular tetramines into Zn<jats:sub>8</jats:sub>L<jats:sub>6</jats:sub> pseudo‐cubic coordination cages. Because of the rectangular, as opposed to square, geometry of the ligand panels, and the possibility of either Δ or Λ handedness of each metal center at the eight corners of the pseudo‐cube, many different cage diastereomers are possible. Each of the six tetra‐aniline subcomponents investigated in this work assembled with zinc(II) and 2‐formylpyridine in acetonitrile into a single Zn<jats:sub>8</jats:sub>L<jats:sub>6</jats:sub> pseudo‐cube diastereomer, however. Each product corresponded to one of four diastereomeric configurations, with <jats:italic>T</jats:italic>, <jats:italic>T</jats:italic><jats:sub>h</jats:sub>, <jats:italic>S</jats:italic><jats:sub>6</jats:sub> or <jats:italic>D</jats:italic><jats:sub>3</jats:sub> symmetry. The preferred diastereomer for a given tetra‐aniline subcomponent was shown to be dependent on its aspect ratio and conformational flexibility. Analysis of computationally modeled individual faces or whole pseudo‐cubes provided insight as to why the observed diastereomers were favored.</jats:p>
Davies JA, Tarzia A, Ronson TK, et al., 2023, Tetramine Aspect Ratio and Flexibility Determine Framework Symmetry for Zn8L6 Self-Assembled Structures, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, ISSN: 1433-7851
Anipa V, Tarzia A, Jelfs KE, et al., 2023, Pore topology analysis in porous molecular systems., R Soc Open Sci, Vol: 10, ISSN: 2054-5703
Porous molecular materials are constructed from molecules that assemble in the solid-state such that there are cavities or an interconnected pore network. It is challenging to control the assembly of these systems, as the interactions between the molecules are generally weak, and subtle changes in the molecular structure can lead to vastly different intermolecular interactions and subsequently different crystal packing arrangements. Similarly, the use of different solvents for crystallization, or the introduction of solvent vapour, can result in different polymorphs and pore networks being formed. It is difficult to uniquely describe the pore networks formed, and thus we analyse 1033 crystal structures of porous molecular systems to determine the underlying topology of their void spaces and potential guest diffusion networks. Material-agnostic topology definitions are applied. We use the underlying topological nets to examine whether it is possible to apply isoreticular design principles to porous molecular materials. Overall, our automatic analysis of a large dataset gives a general insight into the relationships between molecular topologies and the topological nets of their pore network. We show that while porous molecular systems tend to pack similarly to non-porous molecules, the topologies of their pore distributions resemble those of more prominent porous materials, such as metal-organic frameworks and covalent organic frameworks.
Bennett S, Jelfs KE, 2023, Porous Molecular Materials: Exploring Structure and Property Space with Software and Artificial Intelligence, AI-Guided Design and Property Prediction for Zeolites and Nanoporous Materials, Pages: 251-282, ISBN: 9781119819752
Porous molecular materials exhibit permanent porosity in the solid-state; however, unlike network materials such as metal–organic frameworks (MOFs) and zeolites, porous molecular materials lack a continuous network of covalent bonds but are instead formed from the self-assembly of discrete molecules. Porous molecular materials achieve porosity through either an internal cavity in the molecule (intrinsic porosity) or through inefficient packing in the solid-state, such that the molecule is unable to pack in a way that removes all void space (extrinsic porosity). The focus of this chapter will be the application of computational techniques to rationalize the structures and properties of porous molecular materials, including the development of software and artificial intelligence techniques to assist in the understanding and discovery of these systems. The chapter will include a discussion of examples of experimental realization of computational predictions, as well as an analysis of the challenges associated with accelerating the discovery of these materials using artificial intelligence.
Fleck-Kunde T, Wolpert EH, zur LZ, et al., 2022, Observation of Rare Tri6Di9 Imine Cages Using Highly Fluorinated Building Blocks, Organic Materials, Vol: 4, Pages: 255-260
<jats:p>The first synthesis of organic Tri 6 Di 9 cages is presented. Two structurally distinct Tri 6 Di 9 cages were synthesised by combining a highly fluorinated aldehyde with two ditopic amines. Although the pure compounds could not be isolated despite many attempts, the information obtained is critical for the future design of large supramolecular structures. Computational and experimental methods indicate that the addition of perfluorinated aromatic linkers in the assembly of porous organic cages opens up new possibilities for influencing the reaction pathway towards rare and unknown structures.</jats:p>
Wade J, Salerno F, Kilbride R, et al., 2022, Controlling anisotropic properties by manipulating the orientation of chiral small molecules, Nature Chemistry, Vol: 14, Pages: 1383-1389, ISSN: 1755-4330
Chiral π-conjugated molecules bring new functionality to technological applications and represent an exciting, rapidly expanding area of research. Their functional properties, such as the absorption and emission of circularly polarised light or the transport of spin-polarised electrons, are highly anisotropic. As a result, the orientation of chiral molecules criticallydetermines the functionality and efficiency of chiral devices. Here we present a strategy to control the orientation of a small chiral molecule (2,2’-dicyanohelicene, CN6H): the use of organic and inorganic templating layers. Such templating layers can either force CN6H molecules to adopt a face-on orientation and self-assemble into upright supramolecular columns oriented with their helical axis perpendicular to the substrate, or an edge-onorientation with parallel-lying supramolecular columns. Through such control, we show that low- and high-energy chiroptical responses can be independently ‘turned on’ or ‘turned off’. The templating methodologies described here provide a simple way to engineer orientational control, and by association, anisotropic functional properties of chiral molecular systems for a range of emerging technologies.
Wolpert EHH, Jelfs KEE, 2022, Coarse-grained modelling to predict the packing of porous organic cages, CHEMICAL SCIENCE, Vol: 13, Pages: 13588-13599, ISSN: 2041-6520
Jelfs KE, 2022, Computational modeling to assist in the discovery of supramolecular materials, ANNALS OF THE NEW YORK ACADEMY OF SCIENCES, ISSN: 0077-8923
Bechis I, Sapnik AF, Tarzia A, et al., 2022, Modeling the Effect of Defects and Disorder in Amorphous Metal-Organic Frameworks, CHEMISTRY OF MATERIALS, ISSN: 0897-4756
Mroz AM, Posligua V, Tarzia A, et al., 2022, Into the Unknown: How Computation Can Help Explore Uncharted Material Space, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 144, Pages: 18730-18743, ISSN: 0002-7863
Li R-J, Tarzia A, Posligua V, et al., 2022, Orientational self-sorting in cuboctahedral Pd cages, CHEMICAL SCIENCE, Vol: 13, Pages: 11912-11917, ISSN: 2041-6520
Ess DH, Jelfs KE, Kulik HJ, 2022, Chemical design by artificial intelligence, JOURNAL OF CHEMICAL PHYSICS, Vol: 157, ISSN: 0021-9606
Wang A, Tan R, Breakwell C, et al., 2022, Solution-processable redox-active polymers of intrinsic microporosity for electrochemical energy storage, Journal of the American Chemical Society, Vol: 144, Pages: 17198-17208, ISSN: 0002-7863
Redox-active organic materials have emerged as promising alternatives to conventional inorganicelectrode materials in electrochemical devices for energy storage. However, the deployment of redoxactive organic materials in practical lithium-ion battery devices is hindered by their undesired solubilityin electrolyte solvents, sluggish charge transfer and mass transport, as well as processing complexity.Here, we report a new molecular engineering approach to prepare redox-active polymers of intrinsicmicroporosity (PIMs) that possess an open network of sub-nanometer pores and abundant accessiblecarbonyl-based redox sites for fast lithium-ion transport and storage. Redox-active PIMs can be solutionprocessed into thin films and polymer-carbon composites with a homogeneously dispersedmicrostructure, while remaining insoluble in electrolyte solvents. Solution-processed redox-active PIMelectrodes demonstrate improved cycling performance in lithium-ion batteries with no apparent capacitydecay. Redox-active PIMs with combined properties of intrinsic microporosity, reversible redox activityand solution processability may have broad utility in a variety of electrochemical devices for energystorage, sensors and electronic applications.
Ye C, Tan R, Wang A, et al., 2022, Long-life aqueous organic redox flow batteries enabled by amidoxime-functionalized ion-selective polymer membranes, Angewandte Chemie International Edition, Vol: 61, ISSN: 1433-7851
Redox flow batteries (RFBs) based on aqueous organic electrolytes are a promising technology for safe and cost-effective large-scale electrical energy storage. Membrane separators are a key component in RFBs, allowing fast conduction of charge-carrier ions but minimizing the cross-over of redox-active species. Here, we report the molecular engineering of amidoxime-functionalized polymers of intrinsic microporosity (AO-PIMs) by tuning their polymer chain topology and pore architecture to optimize membrane ion transport selectivity. AO-PIM membranes are integrated with three emerging aqueous organic flow battery chemistries, and the synergetic integration of ion-selective membranes with molecular engineered organic molecules in neutral-pH electrolytes leads to significantly enhanced cycling stability.
Perez NH, Sherin PS, Posligua V, et al., 2022, Emerging properties from mechanical tethering within a post-synthetically functionalised catenane scaffold, Chemical Science, Vol: 13, Pages: 11368-11375, ISSN: 2041-6520
Maintaining close spatial proximity of functional moieties within molecular systems can result in fascinating emergent properties. Whilst much work has been done on covalent tethering of functional units for myriad applications, investigations into mechanically linked systems are relatively rare. Formation of the mechanical bond is usually the final step in the synthesis of interlocked molecules, placing limits on the throughput of functionalised architectures. Herein we present the synthesis of a bis-azide catenane scaffold that can be post-synthetically modified using CuAAC ‘click’ chemistry. In this manner we have been able to access functionalised catenanes from a common precursor and study the properties of electrochemically active, emissive and photodimerisable units within the mechanically interlocked system in comparison to non-interlocked analogues. Our data demonstrates that the greater (co-)conformational flexibility that can be obtained with mechanically interlocked systems compared to traditional covalent tethers paves the way for developing new functional molecules with exciting properties.
Wolpert E, Jelfs K, 2022, Coarse-grained modelling to predict the packing of porous organic cages
<jats:p>How molecules pack has vital ramifications for their applications as functional molecular materials. Small changes in a molecule’s functionality can lead to large, non-intuitive, changes in their global solid-state packing, resulting in difficulty in targeted design. Predicting the crystal structure of organic molecules from only their molecular structure is a well-known problem plaguing crystal engineering. Although relevant to the properties of many organic molecules, the packing behaviour of modular porous materials, such as porous organic cages (POCs), greatly impacts the properties of the material. We present a novel way of predicting the solid-state phase behaviour of POCs by using a simplistic model containing the dominant degrees of freedom driving crystalline phase formation. We employ coarse-grained simulations to systematically study how chemical functionality of pseudo-octahedral cages can be used to manipulate the solid-state phase formation of POCs. While presenting a lower computational cost route for predicting molecular crystal packing, coarse-grained models also allow for the development of design rules.</jats:p>
Ye C, Wang A, Breakwell C, et al., 2022, Development of efficient aqueous organic redox flow batteries using ion-sieving sulfonated polymer membranes, Nature Communications, Vol: 13, ISSN: 2041-1723
Redox flow batteries using aqueous organic-based electrolytes are promising candidates for developing cost-effective grid-scale energy storage devices. However, a significant drawback of these batteries is the cross-mixing of active species through the membrane, which causes battery performance degradation. To overcome this issue, here we report size-selective ion-exchange membranes prepared by sulfonation of a spirobifluorene-based microporous polymer and demonstrate their efficient ion sieving functions in flow batteries. The spirobifluorene unit allows control over the degree of sulfonation to optimize the transport of cations, whilst the microporous structure inhibits the crossover of organic molecules via molecular sieving. Furthermore, the enhanced membrane selectivity mitigates the crossover-induced capacity decay whilst maintaining good ionic conductivity for aqueous electrolyte solution at pH 9, where the redox-active organic molecules show long-term stability. We also prove the boosting effect of the membranes on the energy efficiency and peak power density of the aqueous redox flow battery, which shows stable operation for about 120 h (i.e., 2100 charge-discharge cycles at 100 mA cm−2) in a laboratory-scale cell.
Bechis I, Sapnik A, Tarzia A, et al., 2022, Modelling the effect of defects and disorder in amorphous metal−organic frameworks
<jats:p>Amorphous metal−organic frameworks (aMOFs) are a class of disordered framework materials with a defined local order given by the connectivity between inorganic nodes and organic linkers, but absent longer-range order. The rational development of function for aMOFs is hindered by our limited understanding of the underlying structure-property relationships in these systems, a consequence of the absence of long-range order, which makes experimental characterization particularly challenging. Here, we use a versatile modelling approach to generate in-silico structural models for an aMOF based on Fe trimers and 1,3,5-benzenetricarboxylate (BTC) linkers, Fe-BTC. We build a phase space for this material that includes nine amorphous phases with different degrees of defects and local order. These models are analyzed through a combination of structural analysis, pore analysis and pair distribution functions. Therefore, we are able to systematically explore the effects of the variation of each of these features, both in isolation and combined, for a disordered MOF system, something that would not be possible through experiment alone. We find that the degree of local order has a greater impact on structure and properties than the degree of defects. The approach presented here is versatile and allows for the study of different structural features and MOF chemistries, enabling the development of design rules for the rational design of aMOFs.</jats:p>
The development of microporosity in the liquid state is leading to an inherent change in the way we approach applications of functional porosity, potentially allowing access to new processes by exploiting the fluidity of these new materials. By engineering permanent porosity into a liquid, over the transient intermolecular porosity in all liquids, it is possible to design and form a porous liquid. Since the concept was proposed in 2007, and the first examples realised in 2015, the field has seen rapid advances among the types and numbers of porous liquids developed, our understanding of the structure and properties, as well as improvements in gas uptake and molecular separations. However, despite these recent advances, the field is still young, and with only a few applications reported to date, the potential that porous liquids have to transform the field of microporous materials remains largely untapped. In this review, we will explore the theory and conception of porous liquids and cover major advances in the area, key experimental characterisation techniques and computational approaches that have been employed to understand these systems, and summarise the investigated applications of porous liquids that have been presented to date. We also outline an emerging discovery workflow with recommendations for the characterisation required at each stage to both confirm permanent porosity and fully understand the physical properties of the porous liquid.
Sapnik AF, Bechis I, Bumstead AM, et al., 2022, Multivariate analysis of disorder in metal-organic frameworks, NATURE COMMUNICATIONS, Vol: 13
Yuan Q, Szczypiński FT, Jelfs KE, 2022, Explainable graph neural networks for organic cages., Digit Discov, Vol: 1, Pages: 127-138
The development of accurate and explicable machine learning models to predict the properties of topologically complex systems is a challenge in materials science. Porous organic cages, a class of polycyclic molecular materials, have potential application in molecular separations, catalysis and encapsulation. For most applications of porous organic cages, having a permanent internal cavity in the absence of solvent, a property termed "shape persistence" is critical. Here, we report the development of Graph Neural Networks (GNNs) to predict the shape persistence of organic cages. Graph neural networks are a class of neural networks where the data, in our case that of organic cages, are represented by graphs. The performance of the GNN models was measured against a previously reported computational database of organic cages formed through a range of [4 + 6] reactions with a variety of reaction chemistries. The reported GNNs have an improved prediction accuracy and transferability compared to random forest predictions. Apart from the improvement in predictive power, we explored the explicability of the GNNs by computing the integrated gradient of the GNN input. The contribution of monomers and molecular fragments to the shape persistence of the organic cages could be quantitatively evaluated with integrated gradients. With the added explicability of the GNNs, it was possible not only to accurately predict the property of organic materials, but also to interpret the predictions of the deep learning models and provide structural insights for the discovery of future materials.
Tarzia A, Jelfs K, 2022, Unlocking the computational design of metal-organic cages, Chemical Communications, Vol: 58, Pages: 3717-3730, ISSN: 1359-7345
Metal–organic cages are macrocyclic structures that can possess an intrinsic void that can hold molecules for encapsulation, adsorption, sensing, and catalysis applications. As metal–organic cages may be comprised from nearly any combination of organic and metal-containing components, cages can form with diverse shapes and sizes, allowing for tuning toward targeted properties. Therefore, their near-infinite design space is almost impossible to explore through experimentation alone and computational design can play a crucial role in exploring new systems. Although high-throughput computational design and screening workflows have long been known as powerful tools in drug and materials discovery, their application in exploring metal–organic cages is more recent. We show examples of structure prediction and host–guest/catalytic property evaluation of metal–organic cages. These examples are facilitated by advances in methods that handle metal-containing systems with improved accuracy and are the beginning of the development of automated cage design workflows. We finally outline a scope for how high-throughput computational methods can assist and drive experimental decisions as the field pushes toward functional and complex metal–organic cages. In particular, we highlight the importance of considering realistic, flexible systems.
Ning G-H, Cui P, Sazanovich I, et al., 2021, Organic cage inclusion crystals exhibiting guest-enhanced multiphoton harvesting, CHEM, Vol: 7, Pages: 3157-3170, ISSN: 2451-9294
Bennett S, Szczypiński F, Turcani L, et al., 2021, Materials precursor score: modelling chemists' intuition for the synthetic accessibility of porous organic cage precursors, Journal of Chemical Information and Modeling, Vol: 61, Pages: 4342-4356, ISSN: 1549-9596
Computation is increasingly being used to try to accelerate the discovery of new materials. One specific example of this is porous molecular materials, specifically porous organic cages, where the porosity of the materials predominantly comes from the internal cavities of the molecules themselves. The computational discovery of novel structures with useful properties is currently hindered by the difficulty in transitioning from a computational prediction to synthetic realisation. Attempts at experimental validation are often time-consuming, expensive and, frequently, the key bottleneck of material discovery. In this work, we developed a computational screening workflow for porous molecules that includes consideration of the synthetic difficulty of material precursors, aimed at easing the transition between computational prediction and experimental realisation. We trained a machine learning model by first collecting data on 12,553 molecules categorised either as `easy-to-synthesise' or `difficult-to-synthesise' by expert chemists with years of experience in organic synthesis. We used an approach to address the class imbalance present in our dataset, producing a binary classifier able to categorise easy-to-synthesise molecules with few false positives. We then used our model during computational screening for porous organic molecules to bias towards precursors whose easier synthesis requirements would make them promising candidates for experimental realisation and material development. We found that even by limiting precursors to those that are easier-to-synthesise, we are still able to identify cages with favourable, and even some rare, properties.
Kai A, Egleston BD, Tarzia A, et al., 2021, Modular Type III porous liquids based on porous organic cage microparticles, Advanced Functional Materials, Vol: 31, Pages: 1-11, ISSN: 1616-301X
The dispersion of particulate porous solids in size-excluded liquids has emerged as a method to create Type III porous liquids, mostly using insoluble microporous materials such as metal–organic frameworks and zeolites. Here, the first examples of Type III porous liquids based on porous organic cages (POCs) are presented. By exploiting the solution processability of the POCs, racemic and quasiracemic cage microparticles are formed by chiral recognition. Dispersion of these porous microparticles in a range of size-excluded liquids, including oils and ionic liquids, forms stable POC-based Type III porous liquids. The flexible pairing between the solid POC particles and a carrier liquid allows the formation of a range of compositions, pore sizes, and other physicochemical properties to suit different applications and operating conditions. For example, it is shown that porous liquids with relatively low viscosities or high thermal stability can be produced. A 12.5 wt% Type III porous liquid comprising racemic POC microparticles and an ionic liquid, [BPy][NTf2], shows a CO2 working capacity (104.30 µmol gL−1) that is significantly higher than the neat ionic liquid (37.27 µmol gL−1) between 25 and 100 °C. This liquid is colloidally stable and can be recycled at least ten times without loss of CO2 capacity.
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