Poly(styrene–divinyl benzene)‐immobilized Fe(III) complex of 1,3‐bis(benzimidazolyl)benzene: Efficient catalyst for the photocatalytic degradation of xylenol orange

A polymer‐supported Fe(III) complex of 1,3‐bis(benzimidazolyl)benzene [PS–Fe(III)BBZNH] was used in the photodegradation of xylenol orange (XO) dye with H₂O₂ under UV irradiation. The catalyst was synthesized and characterized by elemental analysis, and Fourier transform infrared, far‐infrared, and UV–visible–diffuse reflectance spectroscopy, Scanning electron microscopy, Brunauer–Emmett–Teller surface area measurements, thermogravimetric analysis, and magnetic measurements. An octahedral coordination around Fe(III) was confirmed by electronic spectral data, and a decrease in the intensity of the ν_CH2Cl peak in PS–Fe(III)BBZNH was observed compared to the polymer support; this indicated the binding of the ligand to the support. An array of experiments were carried out to assess the influence of various reaction parameters on its photocatalytic performance to ensure maximum dye degradation. The maximum photocatalytic activity was observed at pH 8 with 125 mg of catalyst, 300 ppm of XO, and 200 ppm of H₂O₂ with complete mineralization after 90 min, as confirmed by chemical oxygen demand measurements. Furthermore, the reactions were repeated under sunlight and under dark conditions to check the photocatalytic efficiency of PS–Fe(III)BBZNH. It displayed better catalytic performance compared than the unsupported complex, PS–Cu(II)BBZNH [Cu(II) complex of 1,3‐bis(benzimidazolyl)benzene], and PS–VO(IV)BBZNH [VO(IV) complex of 1,3‐bis(benzimidazolyl)benzene]. PS–Fe(III)BBZNH could be recycled for up to seven runs. A tentative mechanism involving ·OH radical was proposed. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46480.