Biological molecules for the formation and assembly of metal-organic frameworks

Abstract

Metal-organic frameworks (MOFs) are a class of highly porous hybrid materials – consisting of metal ion based nodes and bridging organic linkers, connecting in two or three-dimensional periodic structures. By combining different inorganic and organic building units a variety of structures and properties can be tailored to a range of applications – gas storage and separation, catalysis and biotechnology. Some of these applications require benign building blocks that are biologically compatible or require specific morphology and crystal size.

The first part of the thesis focuses on using biomolecules as the organic constituents in MOFs. Biomolecules attract particular attention because of their diverse metal binding sites, increased biocompatibility along with developing structural and chemical diversity of the material, for example affording chiral frameworks. Three groups of molecules were investigated: nucleotides, nucleic acids and peptides. Various experimental conditions were employed in the quest to establish conditions under which a porous network comprising of one of these biomolecules were formed. One-dimensional crystal morphology of zinc and copper with nucleotides were identified along with a spherical zinc-peptide structure. However, no porous material was discerned in this investigation.

The final part of the thesis explores biomimetic mineralisation of MOFs; utilising biomolecules as organic matrix for the assembly of inorganic materials. Peptides were explored due to their selfassembly and substrate recognition properties that could potential provide high levels of control during the synthesis. Specific peptide sequences that bound to the desired material were highlighted using the phage display technique, a combinatorial biology protocol used to identify binding peptides via a rapid directed-evolution approach. Millions of phages bearing different peptides are exposed to a target material to select the best binding sequence(s) from the genetically engineered library. This thesis demonstrates a successful application of phage display identifying sequence-specific peptides for MOFs and the peptides subsequent successful use in synthesising a crystalline material; experimental conditions were established where a crystalline framework does not form in the absence of the peptide. Additional outcomes emphasised the effect of framework functionality on the identified peptide sequence(s).

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Identifiers

ORCID for Darren Bradshaw: orcid.org/0000-0001-5258-6224

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