H_xZIF-8/TiO₂with a step-scheme heterojunction for visible-light photocatalytic reduction of nitroaromatic explosives

The utilization of solar photocatalytic oxidation technology represents an effective strategy for addressing environmental pollution and energy shortages. To effectively treat nitro pollutants in wastewater from the explosive industry, a novel composite catalyst H₂₀₀ZIF-8/TiO₂ was proposed with an extended visible light corresponding range and enhanced photogenerated carrier utilization. The optimized photocatalytic reaction conditions are determined to be a pH of 4, with the NaBH₄ dosage of 1 mL at 25 mg mL⁻¹ and the catalyst dosage of 200 mg L⁻¹. Under these conditions, the reduction rate of TNP by H₂₀₀ZIF-8/TiO₂ achieves a value of 98.44% within 10 min. The rate constant of 0.412 min⁻¹ is 5.2 times greater than that of TiO₂ and 3.0 times than that of H₂₀₀ZIF-8, demonstrating excellent photocatalytic performance. Characterization of the photoelectric properties and theoretical calculations confirm that the construction of heterojunctions effectively enhances the separation of photogenerated carriers, and based on these, a possible reaction mechanism is put forward. This study offers a novel idea for the design of ZIF-8-based heterojunction photocatalysts, and its high efficiency and green characteristics show broad application prospects in the treatment of wastewater containing nitro explosives.