Improved Photodegradation of Anionic Dyes Using a Complex Graphitic Carbon Nitride and Iron-Based Metal-Organic Framework Material

Introducing heterostructure to graphitic carbon nitrides (g-C₃N₄) can improve the activity of visible-light-driven catalysts for efficient treatment of multiple toxic pollutants in water. Here we report for the first time that a complex material can be constructed from an oxygen-doped g-C₃N₄ and MIL-53(Fe) metal-organic framework using a facile hydrothermal synthesis and recycled polyethylene terephthalate from plastic waste. The novel multi-walled nanotube structure of the O-g-C₃N₄/MIL-53(Fe) composite which enables unique interfacial charge transfer at the heterojunction showed an obvious enhancement in separation efficiency of the photochemical electron-hole pairs. This resulted in narrow bandgap energy (2.30 eV compared to 2.55 eV in O-g-C₃N₄), high photocurrent intensity (0.17 mA cm^-2 compared to 0.12 mA cm^-2 and 0.09 mA cm^-2 in MIL-53(Fe) and O-g-C₃N₄, respectively), and excellent catalytic performance in the photodegradation of anionic azo dyes (95% RR 195 and 99% RY 145 degraded after 4 h, and only a minor change in the efficiency observed after four consecutive tests). These results demonstrate the development of new catalysts made from waste feedstocks that show high stability, ease of fabrication and can operate in natural light for environmental remediation.