Defect‐Engineered Metal–Organic Frameworks via Coordination Competition Induction for Long‐Life Aqueous Zinc–Ion Batteries

Abstract

ABSTRACT Metal–organic frameworks (MOFs) with well‐defined crystalline structures provide ideal platforms for elucidating the intrinsic relationship between structure and electrochemical performance in aqueous zinc–ion batteries (AZIBs). However, the limited number of electrochemically active metal sites in MOFs constrains Zn 2+ storage capacity and reaction kinetics. In this study, a ligand‐competition‐induced defect engineering strategy was adopted, where partial substitution of dicarboxylate ligands with monocarboxylate ligands during the synthesis of Br‐MIL(V)‐47 enables the ordered construction of controllable coordinatively unsaturated V sites. The results indicate that the moderate introduction of unsaturated V sites enhances framework flexibility and spatial buffering, effectively alleviating local structural distortion induced by repeated Zn 2+ insertion/extraction and suppressing structural collapse and irreversible phase transitions. In/ex situ spectroscopic analyses further confirm the reversible structural evolution. The optimized 0.4‐SSA‐TPA cathode demonstrates excellent cycling stability. Experimental and theoretical analyses collectively indicate that the formation of unsaturated V sites induced local electron density redistribution, thereby facilitating reversible redox reactions. This study provides important insights into the precise design of MOF materials toward next‐generation energy storage applications.