Ultrasonic-assisted fabrication of transient photocurrent-enhanced MOF@Fe3O4–TiO2 composites for visible-light-driven formaldehyde degradation

TiO 2 and its composites have drawn extensive focus from researchers on account of their ability to convert formaldehyde into harmless H 2 O and CO 2 under light irradiation at room temperature, along with their low toxicity, simple operation, low cost and reusability. In this study, a MOF@Fe 3 O 4 –TiO 2 photocatalyst with synergistic degradation effects was synthesized via ultrasonic-assisted impregnation method and comprehensively characterized. Results show that this composite can efficiently remove formaldehyde through its self-established adsorption-degradation-reabsorption cycle (85.50 % within 5.5 h; 92.60 % within 24 h). Moreover, it exhibits enhanced transient photocurrent, which not only facilitates the segregation of electrons and holes across Fe 3 O 4 –TiO 2 heterostructure but also promotes generation and transport of photogenerated electrons between the Fe 3 O 4 –TiO 2 heterojunction and MOF, endowing the catalyst with excellent conductivity and full-spectrum-driven photocatalytic activity. Additionally, EPR and stability tests reveal that the composite decomposes formaldehyde to carbon dioxide and water through formation of two reactive oxygen species (•O 2 − and •OH) and demonstrates good stability.