Seeded growth of single-crystal two-dimensional covalent organic frameworks

Abstract

Polymerization of monomers into periodic two-dimensional networks provides structurally precise, layered macromolecular sheets that exhibit desirable mechanical, optoelectronic, and molecular transport properties. Two-dimensional covalent organic frameworks (2D COFs) offer broad monomer scope but are generally isolated as powders comprising aggregated nanometer-scale crystallites. We found that 2D COF formation could be controlled using a two-step procedure in which monomers are added slowly to preformed nanoparticle seeds. The resulting 2D COFs are isolated as single-crystalline, micrometer-sized particles. Transient absorption spectroscopy of the dispersed COF nanoparticles revealed improvement in signal quality by two to three orders of magnitude relative to polycrystalline powder samples, and suggests exciton diffusion over longer length scales than those obtained through previous approaches. These findings should enable a broad exploration of synthetic 2D polymer structures and properties.

Covalent Organic Frameworks: Chemical Approaches to Designer Structures and Built‐In Functions

“…The use of an excess amount of aniline as a monofunctional modulator would lead to the formation of terminal phenylene imine moieties on the crystal surface; this offers a long‐enough period for correcting structural errors, thereby leading to the formation of single crystals. Adding monomers in portions to the reaction system in the presence of seeds enables the growth of micrometer‐sized boronate‐linked 2D COFs such as COF‐10, COF‐5, and TP‐COF . The development of an efficient method to prepare single‐crystal COFs remains challenging.…”

Polymer Networks: From Plastics and Gels to Porous Frameworks

“…Using a transimination reaction to increase the reversibility of imine bond formation, Yaghi and co‐workers obtained a series of three‐dimensional monocrystalline imine‐linked COFs with single crystal sizes up to ≈100 μm . Around the same time, Dichtel and co‐workers synthesized micron sized single crystals of two‐dimensional boronate ester COFs by the seeded growth mechanism …”

Recent Advances in Covalent Organic Frameworks for Catalysis

“…Other approaches involving ionothermal synthesis, room-temperature synthesis and microwave-assisted synthesis have also been exploited. [36][37][38] In addition, room-temperature synthesis is also an important strategy, which mainly containing two approaches, mechanochemical( MC) grinding and solventm ethod at room temperature. [36][37][38] In addition, room-temperature synthesis is also an important strategy, which mainly containing two approaches, mechanochemical( MC) grinding and solventm ethod at room temperature.…”