Dispersing Au nanoclusters on porphyrin-based metal-organic framework photocatalyst for enhanced proton supply to the Fe–N–N  sites in N2 fixation

Establishing an efficient pathway for proton generation and transfer to the N2 adsorption sites remains a significant challenge in developing high-performance photocatalysts for N2 fixation. Herein, a proton delivery pathway to Fe–N–N * sites was established by embedding Au nanoclusters into the pores of three-dimensional porphyrin-based metal-organic frameworks (PCN-221(Fe)). The NH3 production rate of this obtained catalyst achieves 129.2 μmol g−1 h−1. Both experimental and theoretical results confirm that the enhanced activity is induced by the Au NCs interband transitions and the formation of Au–O species from H2O decomposition on the Au NCs surface. These processes lower the energy barrier for *OOH formation, facilitating the proton generation and creating a higher proton concentration around Fe–N–N * sites, thereby promoting the N2 hydrogenation. This work emphasizes the significance of establishing proton transfer pathways to the N2 adsorption sites in designing effecient photocatalysts for N2 fixation. [Display omitted] •The dispersion of Au NCs in MOF facilitates the proton transfer to Fe−N − N * sites.•The mechanism of proton production and transfer was revealed by in-situ DRIFTS.•In-situ XPS and Raman indicate that H2O decomposes on Au NCs forming Au−O.•DFT indicate that Au−O can promote proton generation by lowering the △G*OOH.