Design and Synthesis of Novel Peptide-Metal Organic Frameworks

Abstract

Metal-organic frameworks (MOFs) are a class of crystalline porous materials with extended network structures formed through the reticular assembly of inorganic and organic molecular building blocks through strong coordination bonds. Compared to other porous materials, MOFs offer a high degree of structural diversity as their shape and pore size as well as functionality can tuned by the precise selection and design of their metal centers and organic struts. Due to their high surface areas, pore volumes, and the possibility of introduction of a myriad of chemical functionalities in their structures, MOFs have gained popularity for applications in many fields such as gas storage, catalysis and separation. Peptides are attractive biomolecules to serve as linkers in the construction of MOFs since they are chiral and offer the possibility of introduction of various functional groups in the MOF structure. Natural peptide assemblies play a central role in function and construction of living systems and there has been a substantial interest over the past decade in the design and construction of artificial peptide-based assemblies with targeted structural, physical and chemical properties, with the goal of mimicking natural biological functions. Despite the great advances in the design and synthesis of metal organic frameworks (MOFs), the synthesis of frameworks using peptide linkers is less well explored. Due to the flexible nature of peptides, obtaining a crystalline peptide MOF is highly challenging. Also, many of the current strategies for synthesizing metal peptide frameworks are based on coordination of the C-terminus and N-terminus as well side chains of peptide linkers with single metal ions. These strategies lead to compact, low dimensional and random frameworks that can not be made by the rational design principles of reticular chemistry. In this dissertation, we describe the design and synthesis of novel peptide-based linkers for the construction of peptide-metal organic frameworks. Our strategy is based on synthesizing peptide linkers where both the C-terminus and the N-terminus ends of the peptides have ditopic 1,3-benzene dicarboxylate groups attached to them, thus converting them into tetracarboxylate-based linkers. We describe our work for the synthesis of novel 3D metal-peptide frameworks using our tetracarboxylate peptide linkers. The chelating ability of the carboxylate groups of our tetracarboxylate peptide linkers provides more structural rigidity and stability, and favor the formation of polynuclear clusters with fixed overall coordination geometry and connectivity. The strong bonding between our carboxylate-based peptide linkers and the metal centers of the secondary building units (SBUs) is expected to yield flexible 3D porous peptide MOFs with robust stability, thus opening the door for the development of new biomimetic 3D porous materials for application in various fields such as enzyme-mimicking catalysis, biomolecular recognition and chiral separations.