Porous Dynamic Materials for Energy Applications

The increase in the transport of people and goods is set to continue over the coming years hence the need to develop a safe, economic and clean fuel. Hydrogen is an ideal fuel as it is highly abundant, lightweight and, of increasing importance, its waste product, water is environmentally benign. Hydrogen can be burnt as a fuel in a safe, efficient and controlled manner as demonstrated by its successful use for space technologies.Hydrogen (H2), if produced cleanly and economically, is an ideal clean energy source for the future. However, widespread use - for example in automotive applications - is limited by the lack of a convenient method of H2 storage. Porous organic polymers have potential as storage media: they are based on light elements, have high thermal and chemical stability, and are synthetically versatile. However, the storage of H2 in polymers and other porous materials is made very difficult by the fundamentally weak interactions which exist between gas and sorbent. Another generic challenge to physisorptive H2 storage is the very high surface areas which are required combined with the optimal isosteric heat of adsorption of -15 kJ/mol. It would be highly desirable to construct high surface area materials with binding energies that are intermediate between weak physisorption and strong chemisorption but this goal has remained elusive and requires a fundamental evaluation of potential binding modes and binding motifs. Increased carbon dioxide (CO2) emissions from fossil fuel combustion are a major cause for environmental concern. Current carbon sequestration methods, such as liquid amines or geologic / biospheric sinks may also have detrimental environmental effects (e.g, lowering the pH of the sea) as well as issues regarding long-term life-cycle analysis and sustainability (in the case of liquid amines). A potential method of separation of CO2 from gas streams is the use of chemical and physical adsorption on functionalised microporous polymers. A more challenging problem is the capture and subsequent activation of CO2. Microporous polymers have several advantages; higher surface areas and their synthetic versatility allows for a wide range of diverse functionality which has the potential to enable reactions which may lead to the direct conversion of CO2 into more complex organic molecules (e.g., by artificial photosynthesis). This is a very challenging goal - there are very tough thermodynamic constraints (e.g., compression steps for CO2 recovery can require more energy than is saved ) and some goals (e.g., artificial photosynthesis) require not only new materials but a fresh new look at fundamental modes of action. This research aims to design entirely novel materials for efficient and convenient gas storage and other applications based upon dynamically responsive materials. A large number of materials have been investigated as physisorptive adsorbents including polymers, carbon, fullerenes and nanotubes, zeolites, and metal organic frameworks (MOFs). Organic polymers as storage media have the advantage of being based on light elements, high thermal and chemical stability, scalable synthesis, and synthetic versatility. A generic challenge to physisorptive hydrogen storage is the very high surface areas which are required combined with the optimal isosteric heat of adsorption of 15kJ/mol. The strategy here is to focus upon mechanical methodologies for capturing and storing hydrogen and carbon dioxide suggesting an innovative and original approach.Close collaboration with synthetic research groups is central to this proposal. An iterative loop of modelling and understanding structures is proposed; this enables us to predict interesting materials which can then be synthesized and characterised. This approach has the benefit of potentially instigating the synthesis of materials which would otherwise not have been undertaken.

Collaboration is central; the synthetic groups of Cooper (Liverpool), McKeown (Cardiff), and Schrder (Nottingham) will benefit directly from the theoretical input outlined. Engagement between theory and synthetic groups will be achieved by regular meetings to review and disseminate findings. A network focussing around the theory group will be established with time spent at each institution to ensure full information exchange. This will build upon the existing links that AT has built as part of her URF. The research outlined in this proposal has scope to impact directly upon other members of the Liverpool Materials Chemistry Group (LMCG) influencing the materials targeted for synthesis potentially leading to materials with greater scientific impact. Engagement with researchers within the field of microporous materials and porous materials modelling will be achieved, and impact maximized, by targeting dissemination of results at specialised conferences. Larger, high profile conferences will be attended and presented at to reach wider audiences and to engage with researchers in other fields. The results will be published in high-impact journals. The PDRA will further their understanding of synthetic processes building upon their theoretical training. Additional training will be provided for the PDRA by attending workshops and training days. Input from the high performance computational support staff will be required to support and maximise the computational capacity. Results of the proposed research which can be utilised by others, for example the fully parameterised forcefields for the materials studied will be made available for free download from the Porous Materials Modelling Group website (PMMG). The website is also a useful tool for communication, providing information and support for other researchers in this area. The website will also be utilised to communicate and engage with the public by incorporating information which clearly describes the research. This research lends itself well to diagrams, figures, and videos to demonstrate the structure of complicated 3-D materials. The LMCG was involved with the creation of the ChemTube 3D polymer freely available web site based at the Liverpool aimed at students, lecturers, and practising chemists. We envisage incorporating the web-based simulations of porous materials into the PMMG website as a means of presenting 3-D structures in an interactive way. The structures will be able to be manipulated and show guest motion within porous structures and exhibit the dynamic behaviour of the guest-host relationship. We will also host workshops which will be targeted at broadening the computational approach to materials chemistry. We are currently organising a workshop to be held in collaboration with Accelrys at Liverpool aimed at introducing a computational approach to UK scientists. Liverpool is a key partner in the Knowledge Centre for Materials Chemistry (KCMC) which brings together the materials chemistry expertise across the Northwest Universities. The main focus of the KCMC is to facilitate knowledge transfer between industry and academia and develop collaborative research projects. This provides a mechanism for identifying projects that could access High Performance computing capabilities within STFC. The wide KCMC network of industry contacts in the Energy Transport and sectors will provide a route to disseminate and discuss the research progress and ultimately identify future research collaborators as the technology matures. This will also provide a mechanism to identify additional application areas for the modelling expertise developed. In addition, the KCMC is connected to the Knowledge Transfer Networks (KTNs) ran by the Technology Strategy Board (TSB). Through interacting with the KTNs the KCMC can broaden the dissemination and industry engagement in a targeted manner. Liverpool is also the recipient of a 3.5M EPSRC Knowledge Transfer Account Grant.