In this proposal, we seek to address an unmet need in the synthesis and application of infinite coordination polymer (ICP) nano- and microparticles. Infinite coordination polymers (ICPs) are an important class of materials consisting of organic molecules joined together in a 3D network by metal ions. These networks can be crystalline (commonly referred to as metal-organic frameworks) or amorphous. One common feature of both crystalline and amorphous coordination polymers is their porosity, enabling them to entrap or catalyze reactions with a variety of guests (gases, solvents, or small molecules). Another common feature is the ability to predictably tune the structure and reactivity of the ICP by rationally designing the metal/ligand combination for the desired application. The main disadvantage of current approaches to make ICP particles is the lack of control over polydispersity. This is due to the dynamic nature of the particle seeding and growth process, which leads to a non-uniform particle size distribution. We seek to address this problem by creating novel ICP precursors from highly monodisperse polymers. Commercially-available polymer standards will be modified with chelating ligands that are specific for a desired transition metal cation. In the presence of the correct metal salt precursor, we predict that the polymer will collapse into highly monodisperse seeds, affording particles with very little size variation. This will be an important step towards fabricating ICP particles with more predictable and uniform behavior that is ultimately dictated by their size, for example in sensing and catalysis applications. Another advantage to making ICP particles from polymeric precursors is the ability to employ block copolymers capable of binding different metals. Once we develop an understanding of the behavior of homopolymeric precursors, we will extend our studies to include block copolymer precursors capable of binding two (or more) metal ions at once. This will allow us to access ICP architectures which are currently unknown, such as core-shell or Janus-type ICP particles. We will explore the synthesis of block copolymer precursors the parameter space for forming “dual” ICP particles of different architectures. Ultimately, our goal is to make switchable ICP particles whose catalytic or sensing activity can be turned on and off or otherwise modulated with external stimuli, affording “smart” ICP particles whose capabilities exceed those of ICPs made from monomeric precursors previously described in the literature. These studies will be of importance in the fundamental areas of nanoscale coordination chemistry and nanoparticle synthesis. Furthermore, we will demonstrate that ICP particles fabricated from polymeric precursors possess advantages over ICPs made from monomeric precursors, namely lower polydispersity and the ability to respond to pre-determined external stimuli for specific applications. We will propose a design for an “on-off” switchable ICP particle catalyst which, if successful, would represent the first ever synthesis of a “smart” ICP particle platform.
|Effective start/end date||5/1/15 → 4/30/18|
- Army Research Office (W911NF-15-1-0151)
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