Constructing Heptazine‐COF@TiO2 Heterojunction Photocatalysts for Efficient Photodegradation of Acetaminophen under Visible Light

We firstly synthesized a novel rodlike C=N linked Heptazine-COF through the classical method. And we mixed the TiO₂ nanoparticles via in situ method to prepare a series of Heptazine-COF@TiO₂ hybrid photocatalysts. The heptazine-COF were closely wrapped with the TiO₂ nanoparticles. The hybrid photocatalysts present outstanding photocatalytic performance owing to the wide visible light absorption and fast charge-carrier transfer via photoelectric test. The Heptazine-COF@TiO₂ photocatalysts were employed to photodegrade acetaminophen (AAP) under visible light, All the experiments were conducted 3 times, and the error bars in all the figures are the standard deviation (SD) of replicates. Moreover, we studied the performance of the optimized catalyst system for recycling and universal experiments. The contaminants photocatalytic degradation experiments were carried out in a 250 mL double-walled glass beaker at room temperature, which was controlled by a cooling water recirculation system. For each AAP degradation, 100 mg of the as-prepared catalysts was added to 100 mL AAP (10 ppm) aqueous solution. The optimal sample HT-3 exhibits unprecedented AAP photodegradation rate constant of 0.7582⁻¹ min and high reusability (93.6 %, in the 6^th cycles). This work laid a foundation for the advancement of photocatalysts and will provide a new sight for the practical application of photodegradation technology for micropollutants.

Abstract

Constructing heterojunction photocatalysts are widely applied to boost the photocatalytic activity of materials. Here, a novel covalent organic framework (COF) material with heptazine units was developed and hybridized with TiO₂ nano particles (NPs) to fabricate the Heptazine-COF@TiO₂ photocatalysts for acetaminophen (AAP) photodegradation. The successfully assembled heptazine unit endows the Heptazine-COF with outstanding semiconductor property (optical bandgap is 2.53 eV). The synthesized Heptazine-COF@TiO₂ hybrids is proved to have the heterojunction structure with high visible light activity and fast charge-carrier mobility, and exhibits better performance in photodegradation of AAP under visible light. The excellent photodegradation efficiency (rate constant: 0.758 min⁻¹) and high reusability (rate constant: 0.452 min⁻¹ in the 6^th cycles) of the optimized sample outperform the traditional inorganic photocatalysts and other heterojunction photocatalysts. In addition, these photocatalysts present universal degradation activity for other dyes and antibiotics.

Zum Volltext