Highly Crystalline Polyimide Covalent Organic Framework as Dual-Active-Center Cathode for High-Performance Lithium-Ion Batteries

Abstract

Polyimide covalent organic framework (PI-COF) materials that can realize intrinsic redox reactions by changing the charge state of their electroactive sites are considered as emerging electrode materials for rechargeable devices. However, the highly crystalline PI-COFs with hierarchical porosity are less reported due to the rapid reaction between monomers and the poor reversibility of the polyimidization reaction. Here, we developed a water-assistant synthetic strategy to adjust the reaction rate of polyimidization, and PI-COF (COFTPDA‑PMDA) with kgm topology consisting of dual active centers of N,N,N′,N′-tetrakis(4-amino­phenyl)-1,4-benzenediamine (TPDA) and pyromellitic dianhydride (PMDA) ligands was successfully synthesized with high crystallinity and porosity. The COFTPDA‑PMDA possesses hierarchical micro-/mesoporous channels with the largest surface area (2669 m2/g) in PI-COFs, which can promote the Li+ ions and bulky bis(trifluoro­methanesulfonyl)imide (TFSI–) ions in organic electrolyte to sufficiently interact with the dual active sites on COF skeleton to increase the specific capacity of cathode materials. As a cathode material for lithium-ion batteries, COFTPDA‑PMDA@50%CNT which integrated high surface area and dual active center of COFTPDA‑PMDA with carbon nanotubes via π–π interactions gave a high initial charge capacity of 233 mAh/g (0.5 A/g) and maintains at 80 mAh/g even at a high current density of 5.0 A/g after 1800 cycles.

Highly Efficient Electrochemical Nitrate Reduction to Ammonia in Strong Acid Conditions with Fe2M‐Trinuclear‐Cluster Metal–Organic Frameworks

“…The facilitated redox activities and electron transfer in the Fe 2 Co‐N 2 ‐MOF can be rationalized by the enhanced delocalized conjugation (between lone pair electrons in nitrogen atoms and pi electrons in benzene rings) in the H 4 TPBD ligand. The conjugation‐enabled radical stabilization in similar tetrakis‐benzyl‐1,4‐benzenediamine ligands have been reported in other applications, [44, 45] and the N 2 ‐ligands (benzenediamine derivatives) have also been demonstrated to exhibit more delocalized conjugation features favoring the interfacial electron transfer, which is in contrast to the localized conjugations in N 1 ‐ligands [46] . As a result, the H 4 TPBD (N 2 ‐ ligands) significantly promote the electron transfer within the Fe 2 Co‐N 2 ‐MOF structure, which is beneficial to its electrocatalytic processes, specifically to the eight‐electron transfer processes involved in the NO 3 RR.…”

Covalent Organic Frameworks as Model Materials for Fundamental and Mechanistic Understanding of Organic Battery Design Principles

“…The strategic design of electroactive COFs with integrated redox-functional groups results in prominent redox peaks in cyclic voltammetry and a stable voltage plateau in charge− discharge cycles, 64 crucial for determining battery working potential and understanding COFs' ongoing redox mechanisms via ex situ and in situ characterization techniques.…”

Recent advances in the utilization of covalent organic frameworks (COFs) as electrode materials for supercapacitors

“…Polyimide COFs (PI-COFs) have been demonstrated as promising electrode materials for rechargeable batteries owing to their outstanding stability and abundant redox sites. 73–75 Similarly, PI-COFs are also a class of promising candidates for SCs. For example, Haldar et al incorporated polypyrrole into the pores of an imide-linked COF, IISERP-COF30.…”