Infinite Coordination Polymer Particles from Polymeric Coordinating Precursors
Abstract
ICPs are an important class of materials consisting of three-dimensional networks of organic polyvalent ligands linked via metal ion nodes. These constructs can be crystalline (commonly referred to as metal-organic frameworks) or amorphous. One common feature of both crystalline and amorphous coordination polymers is their high porosity and surface area, which allows them to entrap small molecules or drive reactions with a variety of guests (gases, solvents, or small molecules). Furthermore the structure and reactivity of ICPs can be rationally tuned by designing the metal/ligand combination to target a variety of applications in sensing, signal amplification, small molecule storage and catalysis. Herein, we propose a novel method for preparing such particles in monodisperse form and in way that provides exquisite control over composition, structure and function. The main disadvantage of current approaches to the synthesis of amorphous ICP particles is the lack of control over polydispersity and surface functionality. This is due to the dynamic nature of the particle seeding and growth process, which leads to a fundamentally non-uniform particle size distribution. We propose to address this limitation by creating novel ICP precursors from highly monodisperse coordinating polymers. During the first 12 month period of this effort, we will functionalize readily accessible polymer standards displaying extremely low polydispersity indices (below 1.1) with ligands that specifically coordinate a desired transition metal cation to achieve highly monodisperse ICP particles. These polymers will then be collapsed into highly monodisperse seeds in the presence of the correct metal salt precursor, affording particles with very little size variation. Doing so will require the fundamental study of polymer synthetic modification and intra-polymer interactions that allow us to use a single polymer chain as the sole organic constituent of the ICP particle. The proposed approach will thus be an important step towards fabricating ICP particles with more predictable and uniform properties, ultimately dictated by their size and surface area, such as the ability to adsorb and interact with small molecules, thereby improving the application of ICPs in sensing and catalysis. Another advantage to synthesizing ICP particles from polymeric precursors is the ability to employ block copolymers capable of binding different metals. Thus, in the second 12 month period, we will develop currently unattainable ICP mixed architectures with spatially-defined and programmable chemical compositions, such as core-shell or Janus-type particles. In addition, block-copolymer precursors will allow us to reversibly toggle between different particle morphologies and surface chemistries using orthogonal chemical inputs while maintaining the overall integrity and size monodispersity of the original construct. In the third 12 month period, 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 responsive ICP particles whose capabilities exceed those of ICPs made from monomeric precursors previously described. Overall, these studies will be of importance in the areas of nanoscale coordination chemistry and nanoparticle synthesis, as well as in fundamental polymer science. While several groups have recently geared efforts towards synthesizing nanoparticle constructs from polymeric precursors, we will develop the first study in which synthetic variables are systematically addressed to achieve the first general approach to make monodisperse ICP particles. This will enable a higher degree of tailorability in terms of morphology, size, and chemical properties of ICPs that will ultimately result in novel and improved applications in catalysis and sensing.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 04, 2019
- Source ID
- W911NF1510151
Entities
People
- Chad Mirkin
Organizations
- Army Contracting Command
- Northwestern University
- United States Army