Gas adsorption and separation in porous metal-organic framework

  • Lixia Guo

Student thesis: Phd

Abstract

This thesis is dedicated to the development and evaluation of efficient methods for mitigating greenhouse gas emissions and reducing global energy consumption to contribute net zero carbon emissions goal. This endeavour involves exploring alternative gas fuels as a substitute for fossil fuels, and with efforts to decrease global energy consumption by employing advanced separation technology. Specifically, this research spotlights the potential of porous metal-organic frameworks (MOFs) for the storage of ammonia (NH3) and the purification of olefins. This thesis also presents an in-depth examination of the impact of host-guest interactions on the efficiency of gas storage and ability to achieve efficient separation. The ultimate goal is to utilise these findings in the design of improved materials for future applications in clean energy storage and gas purification. Chapter 1 provides a comprehensive literature review focusing on two key areas: the economies of ammonia (NH3) and light olefins (C2H4 and C3H6). The chapter explores the host-guest interactions and separation mechanisms involved in the storage of NH3 and the purification of olefins using metal-organic frameworks (MOFs). It examines how these interactions and mechanisms influence the performance of MOFs in terms of NH3 storage and olefin purification. The review aims to establish a solid foundation for understanding the current state of research in this field and identify potential areas for further investigation and improvement. Chapter 2 provides an overview of the aims, objectives, and strategy of MOFs selection for ammonia adsorption and olefin purification. This chapter introduces a range of robust MOFs including Al-MOFs, Sc-MOFs, Zr-MOFs, In-MOFs and Cu-MOFs in these two areas. This chapter further provides a summary of the results from the experiments conducted on these selected MOFs, which demonstrates the significant impact that pore size, shape, and functional groups can have on the efficiency of MOFs for ammonia adsorption and olefin purification, providing valuable insights into the properties of a wider range of MOFs and their potential applications for gas adsorption and separation. This thus leads to our works on the NH3 adsorption in chapter 3 and 4, as well as on olefin purification in chapter 5. Chapter 3 describes an efficient NH3 adsorption in a robust MIL-160. The effects of functional groups (e.g., u2-OH), pore geometry and structural flexibility on the selected Al-based MOFs have been studied for NH3 adsorption. MIL-160 shows high uptakes of NH3 of 4.8 and 12.8 mmol g-1 at both low and high pressure (0.001 and 1.0 bar, respectively) at 298 K, owing to its suitable pore size, anchored u2-OH, and the O-heteroatom of the furan linker. Dynamic breakthrough experiments confirm its excellent ability to capture NH3 with a dynamic uptake of 4.2 mmol g-1 at 1000 ppm. The study of host-guest interactions reveals the preferred adsorption domains of NH3 molecules and an unusual distortion of the local structure of [AlO6] moieties. Considering its high NH3 affinity and uptakes, and high stability, MIL-160 has a great potential in practical application as a robust sorbent for NH3. Chapter 4 describes an exceptional NH3 adsorption in a robust MFM-300(Sc). At 273 K and 1.0 bar, MFM-300(Sc) shows an exceptional NH3 uptake of 19.5 mmol g-1. In situ neutron powder diffraction (NPD), inelastic neutron scattering (INS), synchrotron infrared micro-spectroscopy (SRIR) and solid-state nuclear magnetic resonance (ssNMR) reveal the reversible host-guest and guest-guest hydrogen bond interactions between NH3 and MFM-300(Sc). The moderate strength of the host-guest interaction in MFM-300(Sc) leads to excellent adsorption reversibility and stability with full retention of the capacity over 90 cycles. Chapter 5 describes the efficient purification of C2H4 and C3H6 from mixtures of C2H6/C2H4 and C3H4/C3H6 in MFM-300(In). Single-component adsorption isotherms reveal that MFM
Date of Award31 Dec 2023
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorMartin Schroder (Supervisor) & Sihai Yang (Supervisor)

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