Visible-light-driven zeolite imidazolate frameworks-8@ZnO composite for heavy metal treatment

Hexavalent chromium Cr(VI) is a well-known heavy metal widely existing in wastewater due to various anthropogenic activities. Cr(VI) ions are not biodegradable and tend to be toxic both in flora and fauna. Therefore, effective removal of Cr(VI) has become a very important procedure for treating Cr(VI)-containing wastewater. Here, we developed a facile strategy for constructing ZnO sheets with defective zeolite imidazolate frameworks-8 (ZIF-8) to form visible-light-driven ZIF-8@ZnO composite for efficient photoreduction of Cr (VI). It is widely accepted that both neat ZnO and ZIF-8 show no visible-light photocatalytic activity. However, our study demonstrates that a wide visible-light absorption band is observed in defective ZIF-8@ZnO after introducing self-defects in ZIF-8. Moreover, this strategy of visible-light Zn-based composite photocatalysts can also be used to design other photocatalytic materials for heavy metal treatment.