Engineered zeolitic imidazolate frameworks for water remediation via advanced oxidation processes: from rational design to application

Abstract

This doctoral thesis addresses the pressing challenge of water pollution by organic contaminants and microorganisms through the development of advanced, sustainable treatment technologies. It comprehensively explores the use of zeolitic imidazolate frameworks (ZIFs) as catalytic platforms for heterogeneous photo-Fenton processes, which utilise light and hydrogen peroxide to remediate polluted water. The research is structured across four integrated studies, progressing from fundamental catalyst design to application in real aqueous matrices. The initial work employed a biomimetic strategy to synthesise an iron-modified ZIF-7 (Fe-ZIF-7-III; UPO-4), which demonstrated exceptional activity for degrading caffeine via a novel, non-radical pathway mediated by high-valent iron species. Subsequently, a copper-functionalised ZIF-9 material (Cu-ZIF-9-ica; UPO-3) was developed. The incorporation of copper and a functionalised linker significantly enhanced visible-light absorption, resulting in a material with markedly superior performance for pollutant degradation. To enhance sustainability, the third study pioneered a solvent-free mechanochemical synthesis for ZIF-9. This greener route produced a catalyst with smaller particle size and higher defect density, which outperformed its solvothermally-synthesised counterpart. Finally, the mechanochemical synthesis of UPO-3 was successfully scaled up. The material proved highly effective for the simultaneous degradation of pollutants and inactivation of pathogens, including antibiotic-resistant bacteria, in complex aqueous matrices. It achieved complete disinfection that met stringent EU reuse standards for highest quality water, demonstrating excellent reusability with minimal metal leaching. Collectively, this work establishes a foundation for the rational design of next-generation MOF photocatalysts. It highlights the synergistic benefits of strategic metal incorporation, ligand functionalisation, and sustainable synthesis methods to bridge the gap between laboratory innovation and practical water treatment solutions.