Woodliffe, John Luke
(2024)
Magnetic framework composites for CO2 capture.
PhD thesis, University of Nottingham.
Abstract
Climate change is possibly the greatest challenge currently facing mankind. Immediate action is required to prevent the most devastating effects, particularly on developing nations. This change is being driven by record levels of atmospheric CO2, largely emitted during electricity and heat production. A promising solution is post-combustion carbon capture, which can be retrofitted into existing power stations and allows for the capturing of CO2 at source, removing it from flue gas mixtures. Metal-organic frameworks (MOFs) are highly porous materials consisting of metal ions or clusters linked by organic molecules. MOFs have demonstrated excellent potential for CO2 capture applications due to their high sorption capacities and selectivities for CO2 over other gases. However, MOFs are naturally thermal insulators, making thermal regeneration (emptying the MOF after each adsorption cycle for reuse) challenging, especially on the larger scales required in industrial settings. This limitation can be overcome by forming composites of magnetic materials with the MOFs (magnetic framework composites, MFCs) enabling rapid and energy efficient thermal regeneration by magnetic induction heating.
This thesis describes an investigation into the synthesis of a variety of MFCs (with microsphere and nanoparticle magnetic components, and MOFs HKUST-1, SIFSIX-3-Cu and UTSA-16(Zn)) for CO2 capture by different methods, presented via a collection of manuscripts and associated commentaries. Comprehensive characterisation of materials produced (elucidating structure-property relationships) and analysis for CO2 capture and release performance are contained within the manuscripts.
Chapter 1 (page: 1) first introduces the research area, covering MOFs, MFCs and carbon capture. The associated paper in Appendix 1 (page: 60) reviews the activation and regeneration of MOFs, enabling their high porosities and surface areas to be exploited for sorption applications. Principles of the circular economy and sustainability are considered regarding this process (such as resource and energy efficiency), with a discussion on how these perspectives can inform future developments for MOFs.
Chapter 2 (page: 14) and Appendix 2 (page: 109) describe the production of hierarchically porous MFCs through the layer-by-layer growth of MOFs, specifically HKUST-1 and SIFSIX-3-Cu, on the surface of porous magnetic microspheres (PMMs). A novel flame-spheroidisation route was developed to produce the highly macro-porous PMMs (intraparticle porosity: 95%), which were surface functionalised with molecular and polymeric coatings to facilitate composite formation. Macro-micro hierarchically porous MFCs were then synthesised through a controlled layer-by-layer heterogenous MOF growth strategy (10-11 wt.% MOF loading). This resulted in the first examples of a new material class of MFCs, which contain single-material porous magnetic scaffolds.
Chapter 3 (page: 23) and Appendix 3 (page: 170) explore a microwave-assisted direct growth method for producing MFCs containing citrate-coated Fe3O4 nanoparticles embedded in MOF UTSA-16(Zn). A continuous flow hydrothermal synthesis was first developed to produce magnetic nanoparticles in a single-step, with a comparably very high saturation magnetisation of 78 emu/g due to high purity and crystallinity. These nanoparticles were then incorporated into the MOF via a rapid microwave-assisted direct growth strategy (optimised for the pristine MOF), forming MFCs (3-19 wt.% Fe3O4 in UTSA-16(Zn)) with both high CO2 adsorption capacities (2.8 3.3 mmol/g) and rapid heating ability in an applied magnetic field (reaching 60 °C in 8 seconds), facilitating energy-efficient CO2 release.
Work in Chapter 4 (page: 30) and Appendix 4 (page: 209) builds on the MFCs from the previous chapter (Fe3O4 with UTSA-16(Zn)), developing a solvothermal continuous flow synthesis to produce the MFCs in a sustainable and scalable manner. The reaction is first optimised for the pristine MOF UTSA-16(Zn), resulting in the first reported continuous flow synthesis for the MOF with a 77-fold increase to the production rate (173 g/h) compared to batch methods. The magnetic nanoparticles were then incorporated into the flow synthesis, producing MFCs with high CO2 adsorption capacities (3.1-3.5 mmol/g) in flow (3-11 wt.% Fe3O4 in UTSA-16(Zn)). We report here the highest production rate reported of any MFC to date (152 g/h), a 12-fold increase on the previous record.
Appendix 5 (page: 258) briefly describes alternative applications of the induction heating analysis methods developed for the MFCs, which resulted in two second-author papers. Experiments conducted herein demonstrated the suitability of different magnetic particles for magnetic hyperthermia treatment, targeting a controlled temperature ramp and isothermal hold at 40-45 °C.
Finally, Chapter 5 (page: 39) summarises the overall conclusions of the thesis and recommends directions for future work such as scale-up, pelletisation and magnetic-induction rig testing.
| Item Type: |
Thesis (University of Nottingham only)
(PhD)
|
| Supervisors: |
Laybourn, Andrea
Ahmed, Ifty
Ferrari, Becca |
| Keywords: |
metal-organic framework, magnetite, magnetic nanoparticles, citrate coating, induction heating, MISA, carbon capture, hydrothermal, continuous-flow, adsorption, surface functionalisation, porous microsphere, magnetic framework composite |
| Subjects: |
T Technology > TA Engineering (General). Civil engineering (General) |
| Faculties/Schools: |
UK Campuses > Faculty of Engineering > Department of Chemical and Environmental Engineering |
| Item ID: |
76979 |
| Depositing User: |
Woodliffe, John
|
| Date Deposited: |
18 Jul 2024 04:40 |
| Last Modified: |
18 Jul 2024 04:40 |
| URI: |
https://eprints.nottingham.ac.uk/id/eprint/76979 |
Actions (Archive Staff Only)
 |
Edit View |
Tools
Tools
![[img]](/style/images/fileicons/application_pdf.png)