Precise Regulation of Intra-Nanopore Charge Microenvironment in Covalent Organic Frameworks for Efficient Monovalent
Guoxing Jiang1, Wenwu Zou1, Zhaoyuan Ou1
1Guangdong Provincial Key Laboratory of Fuel Cell Technology, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou, 510641, China.
Abstract:
Charged channels are considered an effective design for achieving efficient monovalent cation transport; however, it remains challenging to establish a direct relationship between charge microenvironments and ionic conductivity within the pores. Herein, we report a series of crystalline covalent organic frameworks (COFs) with identical skeletons but different charge microenvironments and explore their intra-pore charge-driven ion transport performance and mechanism differences. We found that the charged nature determines ion-pair action sites, modes, host-guest interaction, thereby influencing the dissociation efficiency of ion pairs, the hopping ability of cations, and the effective carrier concentration. The order of transport efficiency for Li+, Na+, and H+ follows anion > zwitterion > cation > neutrality. Ionic COFs exhibit up to 11-fold higher ionic conductivity than neutral COFs. Notably, the ionic conductivity of anionic COF achieves 2.0 × 10-4 S cm-1 for Li+ at 30 °C and 3.8 × 10-2 S cm-1 for H+ at 160 °C, surpassing most COF-based ionic conductors. This COF platform for efficient ion migration and stable battery cycling in lithium-metal quasi-solid-state batteries has also been verified as proof of concept. This work offers new insights into the development and structure-activity relationship studies of the next generation of solid-state ionic conductors.
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