Novel direct dual Z-scheme AgBr(Ag)/MIL-101(Cr)/CuFe2O4 for efficient conversion of nitrate to nitrogen

Photocatalytic reduction of nitrate has attracted much attention recently, however, low efficiency and difficult separation have limited its application in practice. In this study, the novel direct dual Z-scheme AgBr(Ag)/MIL-101(Cr)/CuFe2O4 (AB/M/CFO) was fabricated by the hydrothermal technology combined with the photodeposition method for the first time. The AB/M/CFO exhibited the highest nitrate conversion and nitrogen selectivity (79.9% and 94.5%, respectively) compared to AgBr(Ag)/MIL-101(Cr), MIL-101(Cr) and CuFe2O4 for 30 min UV-light irradiation. The dual Z-scheme of AB/M/CFO enhanced electron transfer and charge separation, which was proved by transient photocurrent responses, leading to a significant improvement in photocatalytic efficiency. Meanwhile, after four cycles, the AB/M/CFO photocatalyst also displayed a strong magnetic separation ability and excellent recycling stability. Furthermore, the excitation and electron transfer process over dual Z-scheme AB/M/CFO photocatalytic material were proposed, based on the radical trapping experiments. Our work provides a new strategy to construct dual Z-scheme MOFs-based materials that have promising applications in photocatalytic reduction of pollutants.