Efficient exfoliation of covalent organic frameworks by a facile thiol-ene reaction

Wang, KX; Zhang, H; Xiao, YY; Ren, SJ; Wang, YQ; Li, LY

Abstract

Exfoliating insoluble bulk covalent organic frameworks (COFs) into covalent organic nanosheets (CONs) is an attractive way to improve their processability and the application performance. Herein, we report an efficient thiol-ene-induced exfoliation of oligo (phenylene vinylene) (OPV) based 2D COF-935 into CONs, which exhibits an obvious improvement in the reversible charge/discharge capacity as electrode materials for energy storage devices. The presence of vinylene groups in OPV units allows the addition of thiols under UV irradiation, which weaken the interlayer interactions for exfoliation by breaking the planarity of the layers in COFs. Furthermore, the degree of modification can be quantitatively controlled by varying the feeding ratio to obtain CONs with reasonable pi-conjugation and short lithium-ion transfer distance. Specifically, the CON-UV-1 offers a nearly 90 % higher excellent cycle performance of 494 mA.h.g(-1) at 1 A.g(-1) after 500 cycles and outstanding rechargeability. This research thus provides a promising strategy for the chemical exfoliation of covalent organic frameworks into nanosheets and promotes their potential applications in energy storage.

Keywords: Covalent organic frameworks; Covalent organic nanosheets; Chemical exfoliation; Thiol-ene reaction; Lithium-ion batteries

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