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.