Atmospheric Nitrogen Fixation via a Porous Coordination Polymer Platform with Bridging Dinitrogen Anions

The design of highly electron-active and stable heterogeneous catalysts for ambient nitrogen reduction reaction is challenging due to the inertness of N2 molecule. Herein, we designed and synthesized the first zinc-based coordination polymer with bridging dinitrogen anion ligand, namely NJUZ-1, which is an efficient photocatalyst for atmospheric nitrogen fixation, exhibiting an outstanding ammonia conversion rate of 140 μmol g−1 h−1 and functioning well even with unpurified air as feeding gas. Experimental and theoretical studies revealed that the active “Zn2+-(N≡N)−1-Zn2+” sites can promote the formation of NH3, and the detachment of the yielded NH3 creates unsaturated “Zn2+···Zn+” intermediates, which can be replenished again by external N2 sequestration and fast intermolecular electron migration. The “Zn2+···Zn+” intermediates stabilized by the sandwiched cage-like donor-acceptor-donor framework can sustain continuous catalytic cycles via a pathway analogous to the Mars-van Krevelen process. This work presents a conceptually new strategy for nitrogen fixation via molecular active site catalysts based on metal complexes under mild conditions.