Forming metal organic framework glass membranes for gas separation.
| dc.contributor.author | Stone, Dana M. | |
| dc.date.accessioned | 2025-05-29T00:53:41Z | |
| dc.date.available | 2025-05-29T00:53:41Z | |
| dc.date.issued | 2025 | |
| dc.description.abstract | This thesis investigates the fundamental factors affecting the use of glass transformations to repair defective crystalline metal organic framework (MOF) membranes. This work aims to clarify our understanding of the major limitation that prevents MOF materials being used for gas separation membranes: intercrystalline defects. The research aimed to produce MOF membranes within tubular ceramic supports and evaluate the differences in gas separation performance between crystalline and glass (ag) forms. A four-stage method was adapted to produce glass membranes, including the use of an -alumina tubular support, ZnO precursor deposition via Atomic Layer Deposition (ALD), in-situ solvothermal synthesis of ZIF-62, and defect healing through glass transformation. The gas separation performance of ZIF-62 and agZIF-62 membranes showed low permeance (10⁻⁸ & 10⁻¹⁰ mol m⁻²s⁻¹Pa⁻¹ respectively) and selectivities (e.g. H₂/CO₂ of 3.5 & 4.3 respectively) which were seen as significant areas for improvement. To address the low permeance, ALD conditions to control membrane thickness were developed, reducing crystalline membranes thicknesses from 38 μm to 16 μm. The glass transition process led to further membrane thinning, down to 2 μm, due to a capillary effect. To address low selectivity, the relationship between isothermal hold times, porosity, and macroscopic melting was examined via PALS, adsorption studies, and visual imaging. These results showed that only limited retention of porosity was possible, and that isothermal treatments offered no control over pore structure. These results highlighted challenges in reproducibility during glass transformation by revealing the variability in agZIF-62 samples, including pore aperture size which ranged from 3.2 to 3.7 Å. Finally, a pioneering alternative synthesis approach using chemical vapor deposition (CVD) was explored for the multi-ligand ZIF-62 to address the poor quality of ZIF-62 membranes. However, the polymorphic nature and high energy state of ZIF-62 prevented its synthesis via CVD, instead resulting in the formation of the dense ZIF-zni. Overall, this research provides foundational insights for enhancing the performance and scalability of ZIF-based membranes for gas separation. | |
| dc.identifier.uri | https://hdl.handle.net/10092/108485 | |
| dc.language | English | |
| dc.language.iso | en | |
| dc.rights | All Right Reserved | |
| dc.rights.uri | https://canterbury.libguides.com/rights/theses | |
| dc.title | Forming metal organic framework glass membranes for gas separation. | |
| dc.type | Theses / Dissertations | |
| thesis.degree.discipline | Chemical Engineering | |
| thesis.degree.grantor | University of Canterbury | |
| thesis.degree.level | Doctoral | |
| thesis.degree.name | Doctor of Philosophy | |
| uc.bibnumber | in1412323 | |
| uc.college | Faculty of Engineering |