Cu-MOF/Iodine Synergistic Electrochromic System for Energy-Efficient Smart Windows

The electrochromic behavior of reversible iodine electrodeposition is governed by the coupled kinetics of interfacial charge transfer and species diffusion, yet soluble polyiodides induce a severe shuttle effect, limiting device durability. Herein, through an interface–electrolyte synergistic strategy, we construct a Cu-MOF (HKUST-1) host interface and a water-in-salt electrolyte system to regulate iodine redox electrochemistry. The unsaturated copper coordination sites of HKUST-1 chemically anchor polyiodides to suppress the shuttle behavior, and the reversible redox activity of Cu2+ sites provides additional electron transfer pathways for iodine conversion. Impressively, this system achieves voltage-selective spectral modulation covering visible and near-infrared regions via a preoxidation pathway. The modified electrode delivers an optical contrast of 87.37% at 1100 nm and 91.41% at 550 nm, retaining 89.06% of its optical contrast after 6000 cycles, showing promise for smart window applications. This multifunctional and low-cost strategy provides a unique pathway for systems plagued by soluble intermediates.