One Doping, Dual Amplification: A Spin State‐Charge Transfer Feedback in B‐Doped FeMOF for Synergistically Enhancing Both N₂ Activation and Its Conversion to Ammonia

Photocatalytic N 2 fixation is bottlenecked by the inert activation of N≡N bond and inefficient photogenerated charge utilization. Herein, a boron dopant strategy is reported, via the construction of B‐O‐Fe bridges in an Fe‐MOF, achieving a dual optimization of the Fe‐center electronic spin state and ligand‐to‐metal charge transfer (LMCT) effect, thereby promoting the activation and conversion efficiency of N 2 . Significantly, the activated intermediate‐spin Fe 2+ state serves as a highly efficient electron‐accepting architecture for LMCT, while the accelerated LMCT process, in turn, dynamically sustains the population of this high‐activity site, thus synergistically overcoming the key kinetic barrier of the catalytic cycle. This enables N 2 conversion to NH 3 with a lowered energy barrier for the rate‐determining *NNH → *NNH 2 step. As a result, the B‐doped FeMOF delivers an exceptional N 2 fixation rate of 341 µmol·g −1 ·h −1 under full‐spectrum light, 1.7‐fold higher than its pristine counterpart, and retains over 90% of its efficiency after five cycles. This work presents a scalable and sustainable strategy for photocatalytic N 2 fixation, offering profound insights into the interplay between electronic structure and charge transfer processes.