Dual-Metal MOFs with High Proportion of Mo-Coordinated Zr–O Clusters for Promoting N₂ Fixation

Activation of the N≡N bond is of importance in photocatalytic nitrogen (N2) fixation, which strongly relies on the precise construction of catalytic active sites. Herein, we reported a dual-metal photocatalyst of Mo/UN(Zr) with a high proportion of Mo-coordinated Zr–O clusters (Zr–O–Mo dual-metal active sites) for photocatalytic N2 fixation, which was synthesized though post-modification to the defects of UN(Zr) by Mo. By contrast with the dual-metal photocatalyst of UN(Zr–Mo) synthesized via the co-mixing method, Mo/UN(Zr) possesses a higher proportion of Zr–O–Mo dual-metal active sites that is crucial for activating and polarizing N≡N bond as evidenced by in situ Fourier transform infrared (FTIR) spectroscopy combined with density functional theory (DFT) calculations. The synergistic effect of Zr–O–Mo dual-metal active sites resulted in a lower potential activation energy barrier for N2 activation which promoted the photocatalytic N2 fixation efficiency. The optimum photocatalytic N2 fixation rate of Mo/UN(Zr) was 255.7 μmol g–1 h–1 by adjusting the loading amount of Mo, which was enhanced about 2.5 times and 1.6 times compared with UN(Zr) and UN(Zr–Mo) photocatalyst, respectively. Our study will afford valuable guidance for designing efficient photocatalysts for photocatalytic N2 fixation.