Stimuli-Induced Structural Transformations of Metal–Organic Cages

Nature offers a rich source of inspiration through its use of dynamic structures that respond adaptively to external stimuli. In particular, biological systems rely on precise, stimuli-induced structural changes to regulate complex functions such as molecular recognition, transport, and catalysis. Inspired by these systems, metal–organic cages (MOCs) have emerged as versatile synthetic platforms capable of undergoing controlled transformations in response to diverse stimuli. Studying the structural responsiveness of MOCs not only deepens our understanding of dynamic self-assembly but also lays the groundwork for the development of smart materials with tailored functionalities, including molecular sensing, targeted delivery, and extractions. This thesis focuses on the design and synthesis of stimuli-responsive MOCs, exploring how stimuli drive structural reorganization and bring potential applications. Three distinct MOC systems which can respond to different stimuli were developed and studied. The first system involves photo-responsive azobipyridine ligands that selectively bind five Li⁺ ions in a sandwich structure formed by two pentagonal ligands. Light-induced isomerization from trans to cis disrupts the structure, triggering Li⁺ release. This reversible process enables selective extraction from mixtures containing Na⁺ and K⁺ and photo-release of Li⁺. The second work describes the construction of FeII-based barrel-shaped cages–trigonal antiprisms and square antiprisms–assembled from boron-containing tritopic ligands, where cage topologies were dictated by steric hindrance and coordination geometry. The FeII 6L6 structure selectively encapsulates perfluorosulfonate pollutants, while the FeII 8L8 cage, built using azopyridine units, undergoes reversible redox-triggered disassembly. The third system explores the use of a novel tetrakis(formylpyridine) subcomponent with anilines and ZnII ions to form various MOCs. By tuning metal-to-ligand ratios, homoleptic pseudocubic and open trigonal prismatic cages can be obtained. Post-assembly modification of homoleptic precursors with a tritopic subcomponent affords a heteroleptic capped prism, which is capable of encapsulating pollutants such as perfluorobutanesulfonate and tetracyanoquinodimethane. This demonstrates the subcomponent’s versatility for creating diverse and responsive cage architectures. These studies collectively highlight how diverse stimuli, including light, redox potential, and coordination environment, can be harnessed to modulate MOC structures and functions.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2025

Author dc:creator

• Du, Yuyin

Advisor dc:contributor.advisor

• Nitschke, Jonathan

• Supramolecular Chemistry
• Self-assembly
• Coordination Cage
• Metal-Organic Cage

Licence

• https://www.repository.cam.ac.uk/bitstreams/f10952b7-2a7c-481c-819e-66fad327a7b9/download
• http://purl.org/NET/rdflicense/allrightsreserved

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.125747

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/396449