Breathing Bimetallic MOF Confined Polyoxometalates for Hydration Layer Loosening and Electronic Redistribution Toward Efficient Nitrate Electroreduction and Zn−Nitrate Batteries
Qiushuang Jiang, Xinming Wang, Chao Wang, Shengji Tian, Nan Zhao, Haijun Pang, Chade Lv, Zhipeng Yu, Hong‐Ying ZangABSTRACT
The traditional Haber‐Bosch method suffers from harsh conditions and high energy consumption, while electrocatalytic nitrate reduction to ammonia (ENRA) is a green route for ammonia synthesis and can serve as a cathode reaction for Zn−nitrate batteries. Its development is limited by sluggish intermediate hydrogenation and severe hydrogen evolution reaction (HER). Herein, we develop topology‐engineered isomeric polyoxometalate (POM)‐confined bimetallic metal‐organic framework (MOF) electrocatalysts (NH 2 ‐MIL‐53, ‐88, ‐101). Flexible NH 2 ‐MIL‐88(FeNi) enables tight encapsulation of [PW 12 O 40 ] 3− (PW 12 ) clusters via the “breathing effect”, yielding PW 12 @NH 2 ‐MIL‐88(FeNi) with synergistically modulated electronic distribution and proton transfer. Combined experimental and theoretical studies reveal that confined PW 12 induces electronic redistribution over Fe/Ni centers, concurrently strengthening NO 3 − adsorption on Fe and accelerating *NO 2 hydrogenation on Ni. Beyond electronic effects, PW 12 loosens the rigid hydration layer and forms conjugated acid‐base pairs with MOF amino groups, promoting proton diffusion, boosting *NO 2 hydrogenation, and suppressing HER. Thus, PW 12 @NH 2 ‐MIL‐88(FeNi) achieves an NH 3 yield rate of 20.1 mg h −1 mg cat. −1 with a Faradaic efficiency of 98.6% under neutral electrolytes. When used as a cathode in rechargeable Zn−nitrate batteries, it delivers a peak power density of 13.2 mW cm −2 . This study establishes a generalizable paradigm for engineering interfacial proton transport and electronic properties via POM confinement in MOFs.