A 3D Metal-Organic Framework Protective Layer with Size-Selective Channels and Zincophilic Sites for Highly Stable Zinc Metal Anodes.

Aqueous zinc-ion batteries possess intrinsic operational safety, low cost and scalable application potential, making them promising candidates for large-scale energy storage. However, Zn metal anodes still suffer from severe dendrite proliferation, hydrogen evolution, interfacial corrosion, and inevitable by-product accumulation. The uncontrolled ion flux and distorted electric field further deteriorate the electrochemical durability and cycling lifespan. Targeting these challenges, a multifunctional interfacial protection strategy is proposed to regulate ion transport behavior and suppress parasitic reactions via constructing a 3D Zn(btec) metal-organic framework protective layer on Zn foil through a facile doctor-blade coating method. The as-designed Zn(btec) features uniform subnanometer channels of approximately 5 Å and carboxylate-rich pore walls, which jointly regulate Zn2+-dominated interfacial transport through spatial confinement and pore-wall electrostatic/coordination interactions, thereby suppressing local Zn2+ accumulation and guiding uniform Zn nucleation/deposition. Benefiting from such structural advantages, the Zn(btec)@Zn anode achieves ultra-long stable cycling over 1100 h at 4 mA cm-2 and 1 mAh cm-2 in symmetric cells, and maintains a high Coulombic efficiency of 99.8% beyond 3000 cycles in asymmetric cells. Combined experimental characterizations, finite-element simulations and theoretical calculations verify that the Zn(btec) interphase homogenizes interfacial electric field and Zn2+ flux and reduces interfacial activation energy. When matched with MnO2 or CaV6O16·2.7H2O (CaVO) cathodes, the protected Zn anode enables full cells with improved rate capability and cycling stability. Moreover, the assembled flexible pouch-cell module with an output voltage of 5.4 V can steadily drive a 5 V LED, demonstrating favorable application prospect. This work offers a multifunctional MOF interfacial engineering strategy integrating ion sieving, zincophilic regulation and side-reaction inhibition, and provides the insights into the rational design of highly reversible Zn metal anodes for advanced zinc-ion batteries.