Recyclable photocatalyst composites based on Ag₃VO₄ and Ag₂WO₄ @MOF@cotton for effective discoloration of dye in visible light

Photocatalysts are highly applicable in treatment of the water pollution. However, most of the applied photocatalysts suffer from the inapplicability and non-recyclability which limited their application. Herein, applicable and recyclable effective photocatalyst composites of Ag₂WO₄@MIL-125-NH₂@cotton and Ag₃VO₄@MIL-125-NH₂@cotton successfully prepared by direct synthesis of MIL-125-NH₂ and Ag₂WO₄ or Ag₃VO₄ within the cotton fabric as supported template, sequentially. Agglomerated rock structure of Ag₂WO₄@MIL-125-NH₂ and smaller particles of Ag₃VO₄@MIL-125-NH₂ formed onto the cotton. The prepared composites applied as photocatalysts in the degradation of Methylene Blue (MB) and Rhodamine B (RhB) dyes in the visible light. The highest photodegradtion of dyes observed for Ag₂WO₄@MIL-125-NH₂@cotton and Ag₃VO₄@MIL-125-NH₂@cotton composites because of their low optical band gaps (2.36 eV and 1.87 eV) and their quenching in luminescent spectrum which helped in the ease transfer of photoexcited electrons. The rate constant (k₂) for the photodegradation of MB (RhB) dye reduced significantly from 1.78 × 10^–3 (2.8 × 10^–3) L/mg min to 0.43 × 10^–3 (1.04 × 10^–3) L/mg min and 0.29 × 10^–3 (0.79 × 10^–3) L/mg min, when Ag₂WO₄ and Ag₃VO₄ incorporated in MIL-125-NH₂@cotton composite, respectively. After 4 recycling process, the photodegradation activity of the applied composites diminished from 86–92% (68–80%) to 58–65% (47–54%). The obtained results declared the topmost photocatalytic activity in daylight of the recyclable prepared tri-component composites, reflecting their promising potentials in environmental applications.