Magnetised MOFs – an attractive solution to carbon capture Luke Woodliffe , Amy-Louise Johnston, Ed Lester, Rebecca Ferrari, Ifty Ahmed and Andrea Laybourn Faculty of Engineering, University of Nottingham, Nottingham, NG7 2RD, UK Climate change is possibly the greatest challenge currently facing humankind and immediate action is required to prevent the most devastating effects, particularly on developing nations. 1 An effective mitigation strategy is to decrease CO 2 emissions by capturing the CO 2 from its largest sources, power plants, preventing it from entering the atmosphere. Unfortunately, the current amine absorption technologies have been ineffective due to the very high energy requirements for regenerating the absorbent and separating the CO 2 for storage after capture, increasing a power plant’s energy demand by 25-40%. 2 MOFs (metal-organic frameworks, porous lattices of metal ions/clusters connected by organic linkers) have shown excellent potential for carbon capture due to their high capacities and selectivities for CO 2 . 3 They bind the CO 2 by physical interactions (e.g. electrostatic) rather than chemical bonds, resulting in much lower energies required to regenerate the material and collect the captured CO 2 . However, due to their thermally insulating nature, heating up the materials to regenerate them for reuse is challenging. In this study, new magnetic framework composites (MFCs) have been developed to address this limitation by incorporating magnetic nanomaterials within the MOFs to allow rapid and energy-efficient induction heating of the MFCs for CO2 regeneration. 4 This work details the sustainable synthesis, characterisation and testing of innovative MFCs from inexpensive and widely-available materials. The magnetic materials explored are citrate-coated Fe 3 O 4 nanoparticles, developed in a novel and scalable single-step continuous-flow hydrothermal synthesis. The nanoparticles exhibit very high stability, purity and crystallinity, resulting in much improved room-temperature magnetisation. We then demonstrate the incorporation of various concentrations of these nanoparticles in UTSA-16(Zn) (a zinc and citric-acid based MOF) via a rapid microwave direct-growth strategy to form the MFCs. These show high CO 2 adsorption capacities (2.8-3.3 mmol/g) alongside high magnetisation underambient conditions, allowing the use of low-energy induction heating to heat the MFCs to regeneration temperatures in seconds (e.g. 60°C in 8 seconds). As such, these innovative materials exhibit leading profiles and processing capabilities for carbon capture. The powerful and versatile synthesis routes developed for the nanoparticles and the MFCs are also applicable to other materials/MOFs, enabling paths to a variety of sustainable MFCs for impact across a range of applications.
References 1. IPCC, Climate Change 2014: Impacts, Adaptation, and Vulnerability. Cambridge University Press, Cambridge, UK and New York, NY, USA, 2014. 2. D. M. D’Alessandro, B. Smit and J. R. Long, Angew. Chemie Int. Ed., 2010, 49, 6058–6082. 3. Z. Li, P. Liu, C. Ou and X. Dong, ACS Sustain. Chem. Eng., 2020, 8, 15378–15404. 4. M. M. Sadiq, H. Li, A. J. Hill, P. Falcaro, M. R. Hill and K. Suzuki, Chem. Mater., 2016, 28, 6219–6226.
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