Ester-Linked Crystalline Covalent Organic Frameworks

Abstract

Ester-linked, crystalline, porous, covalent organic frameworks (COFs) have been synthesized and structurally characterized. Transesterification reactions between di-topic 2-pyridinyl aromatic carboxylates and tri-or tetra-topic phenols gave the corresponding ester-linked COFs. They crystallize as 2D structures in kgm (COF-119) and hcb (COF-120, 121, 122) topologies with surface areas of up to 2,092 m 2 /g. Notably, crystalline COF-122 comprises edges spanning over 10 phenylene units; an aspect had only been achieved in metal-organic frameworks. This work expands the scope of reticular chemistry to include for the first time crystalline ester-linked COFs, related to common polyesters.

Synthesis and Polymerization Kinetics of Rigid Tricyanate Ester

“…Figure 2 schematically presents how the target cyanate ester was synthesized. The above synthetic approach follows the well-documented strategy [ 17 , 18 , 19 , 20 ] for obtaining cyanate esters, including those produced industrially.…”

“…Compounds 2–5 were synthesized according to known synthetic protocols described in [ 17 , 18 , 19 ].…”

2D framework materials for energy applications

“…Reactions typically used to fuse the building blocks are condensation reactions to form boroxines 59 and triazines, 60 Schiff base reactions, esterication between diols and boronic acids, 61 and many more. [62][63][64][65][66][67][68] Recently also multicomponent reactions 69,70 have emerged to fuse these structures together, creating more stable bonding units between the building blocks. A common problem among 2D layered COFslow crystallinityarises from the nature of their strong, non-dynamic, covalent bonding, and hence the production of large area 2D COFs through exfoliation of layered COFs is hampered.…”

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

“…In the same year, an imidazole linked COF, chemically comparable to the previously mentioned benzoaxazole linkage, could be obtained by reaction of carboxylic acids and diamines. 52 Finally, very recently the ester, 53 pyrimidazole 54 and polycubane 55 linkages were added to the ever expanding library of COF linkages. Whereas the pyrimidazole linkage was shown to be stable in both 9 M HCl and NaOH, the ester linkage was susceptible to both acids and bases but stable in aqueous environments.…”