A direct Z-scheme Bi₂WO₆/NH₂-UiO-66 nanocomposite as an efficient visible-light-driven photocatalyst for NO removal

To explore an efficient photocatalyst for NO pollution, a direct Z-scheme photocatalytic system is successfully fabricated by coupling Bi₂WO₆ with NH₂-UiO-66 via a simple hydrothermal synthesis technique. The Z-scheme system promotes the NO photocatalytic oxidation activity with an optimum NO removal rate of 79%, which is 2.7 and 1.2 times that obtained by using only pristine Bi₂WO₆ and NH₂-UiO-66, respectively. Simultaneously, superior selectivity for converting NO to NO₃ ^-/NO₂ ^- is observed. The enhanced photocatalytic performance of the Bi₂WO₆/NH₂-UiO-66 hybrids is attributed to the following two aspects: (i) large specific area of NH₂-UiO-66, which exposes more active sites and is beneficial to the adsorption and activation of NO; (ii) outstanding Z-scheme structure constructed between BiWO₆ and NH₂-UiO-66, which can improve the efficiency of the separation of electron-hole pairs and preserves the strong oxidation ability of hybrids. ESR analysis shows that ·O₂ ^- and ·OH contribute to NO removal. A possible photocatalytic mechanism of NO oxidation on the direct Z-scheme photocatalyst (BWO/2NU) under visible light irradiation is proposed. This work displays the BWO/2NU hybrid's potential for treating low-concentration air pollutants, and the proposed Z-scheme photocatalyst design and promotion mechanism may inspire more rational synthesis of highly efficient photocatalysts for NO removal.