Reversible Metal and Ligand Redox Chemistry in Two-Dimensional Iron–Organic Framework for Sustainable Lithium-Ion Batteries

Metal–organic frameworks (MOFs) are emerging as attractive electrode materials for lithium-ion batteries, owing to their fascinating features of sustainable resources, tunable chemical components, flexible molecular skeletons, and renewability. However, they are faced with a limited number of redox-active sites and unstable molecular frameworks during electrochemical processes. Herein, we design a novel two-dimensional (2D) iron­(III)-tetraamino-benzoquinone (Fe-TABQ) with dual redox centers of Fe cations and TABQ ligands for high-capacity and stable lithium storage. It is constructed of square-planar Fe–N2O2 linkages and phenylenediamine building blocks, between which the Fe-TABQ chains are connected by multiple hydrogen bonds, and then featured as an extended π–d-conjugated 2D structure. The redox chemistry of both Fe3+ cations and TABQ anions is revealed to render its remarkable specific capacity of 251.1 mAh g–1. Benefiting from the intrinsic robust Fe–N­(O) bonds and reinforced Li–N­(O) bonds during cycling, Fe-TABQ delivers high capacity retentions over 95% after 200 cycles at various current densities. This work will enlighten more investigations for the molecular designs of advanced MOF-based electrode materials.