Designed synthesis of stable light-emitting two-dimensional sp2 carbon-conjugated covalent organic frameworks

Abstract

Covalent organic frameworks enable the topological connection of organic chromophores into π lattices, making them attractive for creating light-emitting polymers that are predesignable for both the primary- and high-order structures. However, owing to linkages, covalent organic frameworks are either unstable or poor luminescent, leaving the practical synthesis of stable light-emitting frameworks challenging. Here, we report the designed synthesis of sp2 carbon-conjugated frameworks that combine stability with light-emitting activity. The C=C linkages topologically connect pyrene knots and arylyenevinylene linkers into two-dimensional all sp2 carbon lattices that are designed to be π conjugated along both the x and y directions and develop layer structures, creating exceptionally stable frameworks. The resulting frameworks are capable of tuning band gap and emission by the linkers, are highly luminescent under various conditions and can be exfoliated to produce brilliant nanosheets. These results suggest a platform based on sp2 carbon frameworks for designing robust photofunctional materials.

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

“…As a result of their layer structure, COFs can be exfoliated into nanosheets. Exfoliation has been achieved by two methods: sonication in delaminating solvents and mechanical grinding . For example, a suspension of boronate ester linked COF‐8 (1 mg mL −1 ) yielded nanosheets upon sonication in dry CH 2 Cl 2 for 15 min .…”

“…The sp 2 ‐carbon COFs are linked with C=C bonds and enable the construction of skeletons that are fully π‐conjugated along both the x and y directions when a tetragonal topology is developed . Keeping tetraphenylpyrene as a knot and using phenyl, biphenyl, and terphenyl as linkers led to the synthesis of a series of COFs namely sp 2 c‐COF (Figure ), sp 2 c‐COF‐2 (Figure a), and sp 2 c‐COF‐3 (Figure b).…”

Tailoring Covalent Organic Frameworks To Capture Water Contaminants

“…Treatment with NaOH resulted in retention of crystallinity of the COFs while converting the nitrile groups to amide functionalities. Jiang and co‐workers prepared a series of sp 2 carbon‐conjugated COFs through the condensation of an acetonitrile and a benzaldehyde building block . The series showed high crystallinity with minor weight losses after soaking for 7 days in water, concentrated acid, or concentrated base.…”

Kovalente organische Gerüstverbindungen: chemische Ansätze für Designerstrukturen und integrierte Funktionen

“…Aufgrund ihrer Schichtstruktur können COFs zu Nanoblättern exfoliert werden. Exfoliation kann durch zwei Verfahren erfolgen: Ultraschallbehandlung in Delaminationslösungsmitteln und mechanisches Mahlen . So ergibt eine Suspension von boronatesterverknüpftem COF‐8 (1 mg mL −1 ) innerhalb von 15 min Ultraschallbehandlung in wasserfreiem CH 2 Cl 2 Nanoblätter .…”

“…Die sp 2 ‐Kohlenstoff‐COFs sind durch die C=C‐Bindung verknüpft und ermöglichen die Konstruktion von Gerüsten, die, wenn eine tetragonale Topologie eingesetzt wird, entlang der x ‐ wie auch der y ‐Richtung vollständig π‐konjugiert sind . Mit Tetraphenylpyren als Knoten und Phenyl, Biphenyl und Terphenyl als Linker wurden sp 2 c‐COFs (Abbildung ), sp 2 c‐COF‐2 (Abbildung a) und sp 2 c‐COF‐3 (Abbildung b) synthetisiert.…”