Z-Scheme Photocatalytic CO₂ Reduction on a Heterostructure of Oxygen-Defective ZnO/Reduced Graphene Oxide/UiO-66-NH₂ under Visible Light

The construction of a Z-scheme heterojunction is an effective way to isolate photogenerated electron-holes and enhance the activity of the semiconductor photocatalysts. However, the Z-scheme heterojunctions based on metal-organic frameworks were rarely reported. Herein, a novel oxygen-defective ZnO (O-ZnO)/reduced graphene oxide (rGO)/UiO-66-NH2 Z-scheme heterojunction has been prepared by a facile solvothermal route. The morphologies, structures, and photoelectric characteristics of the acquired materials were characterized in detail. The photocatalytic activity of the O-ZnO/rGO/UiO-66-NH2 heterostructure was assessed by photocatalytic CO2 reduction. The results indicated that the O-ZnO/rGO/UiO-66-NH2 heterostructure could efficiently reduce CO2 to CH3OH and HCOOH, and its activity was significantly superior to that of O-ZnO/UiO-66-NH2 and ZnO/rGO/UiO-66-NH2. Under illumination of visible light, the yield of CH3OH and HCOOH over the O-ZnO/rGO/UiO-66-NH2 heterostructure reached 34.83 and 6.41 μmol g-1 h-1, respectively. The high photoactivity of the O-ZnO/rGO/UiO-66-NH2 heterostructure should be caused by the effective spatial separation of photogenerated electrons and holes via a Z-scheme charge transfer. This research may well present an insight into the design and fabrication of novel Z-scheme photocatalytic systems for environmental remediation and energy conversion.