Life Cycle Assessment of Metal Organic Frameworks

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With the increasing need to reduce carbon emissions into the atmosphere, removal of carbon dioxide in flue gas from power plants is being highlighted as a major factor towards this goal. In March 2023, the UK government announced funding for 8 projects across 2 clusters focussing on Carbon Capture and Storage technologies. The current predominant technology is amine solvents, which binds with the CO2 to isolate it from the flue gas, which can then be removed through a reversible reaction to allow the CO2 to be stored safely and the amines to be used again. However, this regeneration of the solvent is highly energy intensive, and the degradation of amines releases waste products that are harmful to the environment.An alternative technology that has been gaining greater exposure in recent years are MOFs (metal organic frameworks), which are regular cage-like structures of metal ions and organic linkers which trap CO2, and can then be emptied for storage and the MOF used again. Based on the current TRL for this technology, it is still much more expensive than amines, but as costs come down, it is being seen as the most viable option to replace amines. The regeneration energy is much lower, and there is very little waste product that is harmful to the environment, with the possibility of being completely recyclable.As MOFs are still relatively new, there is little research to corroborate these claims, so this project will involve mapping the life-cycle of MOFs, from their initial manufacture to their use, and finally to their disposal or recycling into new MOF materials, to allow an effective comparison of the reduction in harmful environmental impacts and greater energy efficiency of the technology compared to current market equivalents.This will be done by conducting an LCA (life-cycle assessment), a standardised method for assessing a product or service from the acquisition of raw materials through to disposal, laying out the working process in 4 main stages (goal and scope, inventory, impact assessment, interpretation) that can then be used to track the mass quantities, energy balances and environmental impacts of that product or service over its complete life cycle. There are only 2 such studies for MOF CC and for only specific materials and manufacturing processes, so creating a complete and detailed model that can be applied to numerous MOFs would be beneficial. From here, the model will be expanded to include more processes and details, as well as being converted to a larger, industry-scale model.There are also a number of factors which affect the long-term use of MOFs which need to be tested and analysed. The two main parameters for use of MOFs are temperature and pressure, since the MOF must be heated to roughly 100oC to perform adsorption, and the CO2 is removed by applying a vacuum to the material. As such, the physical degradation of MOF against these factors needs to be studied, to determine the length of time the material can be used for effectively before requiring disposal or recycling. Rigs are being designed and tested to validate temperature and/or pressure swing to determine how robust each MOF is during prolonged use.