Metal organic framework decorated with molybdenum disulfide for visible-light-driven reduction of hexavalent chromium: Performance and mechanism

This work demonstrates that the photoreduction of hexavalent chromium using iron-based metal organic framework was able to be enhanced through doping molybdenum disulfide. The 1.5 wt % molybdenum disulfide doped iron-based metal organic framework exhibited the best photocatalytic activity towards hexavalent chromium reduction with an efficiency of 98.8% over 60 min, accompanied by remarkable repeatability and stability. The enhancement of photocatalytic efficiency could be achieved by (i) relieving the recombination process of photogenerated carriers in iron-based metal organic framework resulting from the formation of heterojunction, (ii) reducing photogenerated electrons transfer resistance from the interior to the surface of iron-based metal organic framework because of favorable electron transfer of molybdenum disulfide, and (iii) regulating the positive charge distribution on the surface of iron-based metal organic framework. Importantly, nanosecond time-resolved transient absorption spectroscopy further disclosed that the doping of molybdenum disulfide fundamentally improved the utilization of photogenerated electrons. This work evidences the important role of heterojunction from a microscopic perspective, which provides inspiration for the preparation of highly-efficient environmental functional photocatalysts based on iron-based metal organic frameworks.