In-situ directional growth of NH2-MIL-125(Ti) induced by diatomite enhances the quantum efficiency of CO2 photoreduction with water vapor.

Photocatalytic CO2 reduction harnesses sunlight to convert CO2 into fuels (e.g., CO, CH4) to address global warming and energy shortages, but faces challenges like high cost and low efficiency. In this work, NH2-MIL-125(Ti)/diatomite composites were prepared by one-step solvothermal method using diatomite as a support. Characterization indicated that NH2-MIL-125(Ti) units were grown in-situ on diatomite through surface-mediated interactions with Si-O-Ti bonds. This process significantly reduced the agglomeration of NH2-MIL-125 particles. Among the resulting composites, NH2-MIL-125/DE-60 % had the best photocatalytic activity with a CO production rate of 7.36 μmol g-1 h-1, which is 1.56 times higher than NH2-MIL-125. In four cycles, the yield remained above 6.88 μmol g-1 h-1. Meanwhile, electrochemical characterization revealed that composite enhances the separation efficiency of photogenerated carriers and reduces carrier migration resistance. The excellent performance of NH2-MIL-125/diatomite composites could be attributed to the synergistic effects of its better dispersion and the Si-O-Ti interface formation, which improve light absorption, increase the number of active sites and facilitate charge separation. Meanwhile, the specific mechanism of CO2 reduction by NH2-MIL-125/diatomite composites and its reduction pathway were also revealed. In conclusion, this study successfully reduced the agglomeration effect of MOFs, and provided implications for realizing in-situ growth of MOFs on mineral surfaces.