Synergistic Effect of Oxygen Vacancy and High Porosity of Nano MIL‐125(Ti) for Enhanced Photocatalytic Nitrogen Fixation

This work reports that a low-temperature thermal calcination strategy was adopted to modulate the electronic structure and attain an abundance of surface-active sites while maintaining the crystal morphology. All the experiments demonstrate that the new photocatalyst nano MIL-125(Ti)-250 obtained by thermal calcination strategy has abundant Ti³⁺ induced by oxygen vacancies and high specific surface area. This facilitates the adsorption and activation of N₂ molecules on the active sites in the photocatalytic nitrogen fixation. The photocatalytic NH₃ yield over MIL-125(Ti)-250 is enhanced to 156.9 μmol g^-1 h^-1 , over twice higher than that of the parent MIL-125(Ti) (76.2 μmol g^-1 h^-1 ). Combined with density function theory (DFT), it shows that the N₂ adsorption pattern on the active sites tends to be from "end-on" to "side-on" mode, which is thermodynamically favourable. Moreover, the electrochemical tests demonstrate that the high atomic ratio of Ti³⁺ /Ti⁴⁺ can enhance carrier separation, which also promotes the efficiency of photocatalytic N₂ fixation. This work may offer new insights into the design of innovative photocatalysts for various chemical reduction reactions.