Insight into the Novel Z-Scheme ZIF67/WO3 Heterostructure for Improved Photocatalytic Degradation of Methylene Blue Under Visible Light

In this work, a novel Z-scheme heterojunction of ZIF67/WO3 nanocomposite is successfully prepared via immobilizing WO3 on the MOFs ZIF67 and confirmed by measuring XRD, FT-IR spectroscopy, XPS, SEM, TEM, and EDS. UV–vis and Mott-Schottky measurements. The photocatalytic activity of the as-prepared ZIF67/WO3 is evaluated by degrading methylene blue (MB) solution under simulated visible light irradiation. Obviously, the optimal ZIF67/WO3-0.3 (designated as 0.3 g addition of WO3) delivers significant photocatalytic degradation exceeding 90% toward MB within 120 min, which is about 3.0 and 4.2 times higher than those of pure ZIF67 (30.0%) and WO3 (21.2%). With the addition of 0.02 g ZIF67/WO3-0.3 composite, a total volume of 50 mL of MB at 10 mg/L was thoroughly degraded in 120 min with an apparent rate constant of 0.0184 min−1. Reactive species scavenging experiments indicated that the holes (h+) and hydroxyl radical (·OH) are mainly responsible for MB degradation. Moreover, the probable reaction mechanism is elucidated by detecting the intermediates by performing LC–MS measurements. The excellent photocatalytic performance of the ZIF67/WO3 is predominantly determined by the structural properties of the composite and the Z-scheme charge transfer pathway, which promote the efficient separation of photogenerated carriers and facilitate the transfer of photogenerated electrons to active sites. Therefore, it is a promising strategy for immobilizing the WO3 on MOFs for constructing Z-scheme heterojunction to degrade the refractory organic dyes.