Defect-Engineered Metal-Organic Frameworks via Coordination Competition Induction for Long-Life Aqueous Zinc-Ion...

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 Zn²⁺ 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 Zn²⁺ 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.