Controlling the crystalline structure of imine-linked 3D covalent organic frameworks

Abstract

We explore the growth mechanism of 3D Covalent Organic Frameworks (COFs) using imine-linked model systems. We confirm that 3D imine COFs crystalize through an amorphous polymer intermediate, whose conditional state is key for preferential generation of the ideal porous structure over the collapsed hydrated form.

Solving the COF trilemma: towards crystalline, stable and functional covalent organic frameworks

“…The structures could be switched based on the presence of water, which leads to a significant contraction of the unit cell due to changes in hydrogen bonding. 4,150 Similar switchable structures are observed with the breathing effect in a 3D COF with THF ( Fig. 25), 149 leading to conformational changes in the structure which influence the distance between the interpenetrated nets as a result of the imine rotation that can be seen as a cause of this flexibility.…”

Micro/Nano‐Scaled Covalent Organic Frameworks: Polymerization, Crystallization and Self‐Assembly

“…Smith explored the growth mechanism of 3D COFs by using imine-linked COF-300 as model systems. [13] Upon initial addition of PDA to the TAPM monomer solution, amorphous solids rapidly form at room temperature in high yields, thus confirmed the 3D COF also crystallizes through an amorphous polymer intermediate.…”

Conquering the crystallinity conundrum: efforts to increase quality of covalent organic frameworks

“…Very little is known about the mechanism of 3D imine COF formation, but it has been proven that the formed amorphous intermediate can be recrystallized to crystalline COF-300. 121 As no layers exist for these 3D structures, the most plausible mechanism is via the amorphous polymer. Moreover, the more open pores, lacking p-p layer interactions are highly susceptible to pore collapse when common activation methods are used.…”