Seeded Growth of Single-Crystal Two-Dimensional Covalent Organic Frameworks

14 December 2017, Version 2
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Polymerizing monomers into periodic two-dimensional (2D) networks provides structurally precise, atomically thin macromolecular sheets linked by robust, covalent bonds. These materials exhibit desirable mechanical, optoelectrotronic, and molecular transport properties derived from their designed structure and permanent porosity. 2D covalent organic frameworks (COFs) offer broad monomer scope, but are generally isolated as polycrystalline, insoluble powders with limited processability. Here we overcome this limitation by controlling 2D COF formation using a two- step procedure. In the first step, 2D COF nanoparticle seeds are prepared with approximate diameters of 30 nm. Next, monomers are slowly added to suppress new nucleation while promoting epitaxial growth on the existing seeds to sizes of several microns. The resulting COF nanoparticles are of exceptional and unprecedented quality, isolated as single crystalline materials with micron-scale domain sizes. These findings advance the controlled synthesis of 2D layered COFs and will enable a broad exploration of synthetic 2D polymer structures and properties.

Keywords

covalent organic frameworks
two-dimensional polymers
crystal engineering
controlled polymerization
self-assembly
crystallization
Chemistry

Supplementary materials

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2017 12 ChemRxiv Evans COF SingleXtal SI
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ChemRxiv
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