Highly Efficient Nitrogen Reduction to Ammonia through the Cooperation of Plasma and Porous Metal–Organic Framework Reactors with Confined Water

Abstract While the ambient N 2 reduction to ammonia (NH 3 ) using H 2 O as hydrogen source (2N 2 +6H 2 O=4NH 3 +3O 2 ) is known as a promising alternative to the Haber–Bosch process, the high bond energy of N≡N bond leads to the extremely low NH 3 yield. Herein, we report a highly efficient catalytic system for ammonia synthesis using the low‐temperature dielectric barrier discharge plasma to activate inert N 2 molecules into the excited nitrogen species, which can efficiently react with the confined and concentrated H 2 O molecules in porous metal–organic framework (MOF) reactors with V 3+ , Cr 3+ , Mn 3+ , Fe 3+ , Co 2+ , Ni 2+ and Cu 2+ ions. Specially, the Fe‐based catalyst MIL‐100(Fe) causes a superhigh NH 3 yield of 22.4 mmol g −1 h −1 . The investigation of catalytic performance and systematic characterizations of MIL‐100(Fe) during the plasma‐driven catalytic reaction unveils that the in situ generated defective Fe−O clusters are the highly active sites and NH 3 molecules indeed form inside the MIL‐100(Fe) reactor. The theoretical calculation reveals that the porous MOF catalysts have different adsorption capacity for nitrogen species on different catalytic metal sites, where the optimal MIL‐100(Fe) has the lowest energy barrier for the rate‐limiting *NNH formation step, significantly enhancing efficiency of nitrogen fixation.