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In nature, nitrogenase can achieve efficient environmental fixation of nitrogen (N 2 ) molecules through π-backbonding mechanism, which inspires us to simulate the N 2 fixation process of nitrogenase to overcome the bottleneck in existing artificial synthetic ammonia (NH 3 ), so as to achieve efficient artificial conversion of N 2 to NH 3 under mild conditions. Herein, we highlight a strategy of constructing a mimic-enzyme catalyst for photocatalytic N 2 fixation based on metal–organic frameworks (MOFs) and polyoxometalates (POMs) in which POMs can efficiently regulate carrier dynamics of MOFs to simulate the π-backbonding mechanism of nitrogenase. Oxygen-rich group POMs with strong electronegativity attract electrons from transition-metal atom in MOFs, thus reducing the 3d orbitals’ electron density of transition-metal atom and enhancing unoccupied d-orbitals in favor of adsorbing N 2 . Simultaneously, the photoexcited electrons in MOFs are efficiently transferred by POMs into the N–N π* antibonding system to activate N 2 via π-backbonding mechanism. Taking MIL-88A (C 12 H 6 O 13 Fe) and PMo 10 V 2 (H 5 PMo 10 V 2 O 40 ) as an example, we have obtained a significantly enhanced NH 3 production rate of 50.82 μmol g –1 h –1, which is enhanced by 6 times for MIL-88A and 14 times for PMo 10 V 2 . Our results make an important contribution to further guidance for artificial N 2 fixation under mild conditions.
Li et al. (Fri,) studied this question.