In Situ Deformation Topology of COFs with Shortened Channels and High Redox Properties for Li–S Batteries

Abstract

Covalent organic frameworks (COFs) with various topologies are typically synthesized by selecting and designing connecting units with rich shapes. However, this process is time-consuming and labour-intensive. Besides, the tight stacking of COFs layers greatly restrict their structural advantages. It is crucial to effectively exploit the high porosity and active sites of COFs by topological design. Herein, for the first time, inducing in situ topological changes in sub-chemometric COFs by adding graphene oxide (GO) without replacing the monomer, is proposed. Surprisingly, GO can slow down the intermolecular stacking and induce rearrangement of COFs nanosheets. The channels of D-[4+3] COFs are significantly altered while the stacking of periodically expanded framework is weakened. This not only maximizes the exposure of pore area and polar groups, but also shortens the channels and increases the redox activity, which enables high loading while enhancing host-guest interactions. This topological transformation to exhibit the structural features of COFs for efficient application is an innovative molecular design strategy.

Sub‐Stoichiometric Covalent Organic Frameworks

“…Recently, the same group introduced an in situ topological modification approach to introduce graphene oxide (GO) into sub‐stoichiometric COFs without the need for monomer replacement. [ 39 ] Remarkably, the incorporation of GO disfavors intermolecular stacking and prompts a reorganization of COFs nanosheets. Abundant unreacted functional groups (i.e., formyl, imine) and accessible pores present in D‐[4+3] COFs/GO composites not only provided high loading and effective anchoring of polysulfides, but also reduced the Li + transport distance and accelerated the electrochemical reaction rate.…”

Covalent Organic Framework Based Lithium–Sulfur Batteries: Materials, Interfaces, and Solid‐State Electrolytes

“…Furthermore, borates, imines, and polarized ethylene bonds have been utilized as coupling strategies for the construction of novel COFs. [97][98][99][100] Nevertheless, these covalent bonds exhibit weak electrical characteristics and little chemical reactivity for catalytic or redox purposes. Xu et al [101] examined the possibility of using a COF to counteract the shuttle effect.…”

“…The insertion of functional groups at the COF junctions is atomically more efficient, despite the difficulties in the synthetic procedure. [98] Haldar et al [68] developed a porous 2D thianthrene-based COF (Figure 5a) through a dynamic, selfcorrecting nucleophilic aromatic substitution process to produce disulfide bonds. This was the first time that the sulfide unit was structurally incorporated into a multilayer crystalline COF.…”

Practical challenges and future perspectives of solid polymer electrolytes: microscopic structure and interface design

“…These structures provide a basis for long-range Li + ion transport. 97,98 Therefore, the introduction of COFs and MOFs into SPEs can lead to the formation of Li + ion channels. However, the application of COFs and MOFs in SPEs has been limited due to the dilution of overall charge-carrier concentration caused by porosity.…”