Novel hierarchical TiO₂@ZIF-8 for photodecolorization of semi-real sample bromothymol blue aqueous solution

A TiO₂@ZIF-8 hierarchical structure built up of a well-ordered array was achieved by an easy handling of Zn(NO₃)₂·6H₂O, 2-methylimidazole and TiO₂ mixture in DMF with solvothermal behavior. It is believed that solvothermal cause to the driving force for the accomplished TiO₂ rod to self-assemble into ZIF-8, which performed as the substrate for secondary heterogeneous nucleation, and afterwards the crystal growth happened into development of a TiO₂@ZIF-8 rod arrangement. The TiO₂@ZIF-8 hierarchical rod array structure was characterized by FTIR, XRD, SEM, EDX, ICP, DRS, TG, NH₃–TPD and BET and employed as photocatalyst for photodecolorization of bromothymol blue (BTB) aqueous solution under Hg lamp irradiation. The optimum values of the experimental parameters which affect the decolorization efficiency were attained as: 0.1 g L⁻¹ of the 7% TiO₂@ZIF-8.30 ppm dye concentration and pH 6.5. The decolorization kinetics was fitted well to the Langmuir–Hinshelwood first-order rate law. It was found that the catalyst displayed significantly high catalytic stability, and the activity loss is appearing after four BTB decolorization cycles. Graphical abstract:

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