Photocatalytic degradation of organic dyes by a donor–acceptor type conjugated polymer: poly(thiophene‐1,3,4‐oxadiazole) and its photocatalytic mechanism

A donor–acceptor conjugated‐type polymer, poly(thiophene‐1,3,4‐oxadiazole) (PThOD), was synthesized by one‐step polycondensation in polyphosphoric acid. PThOD was confirmed and characterized using Fourier transform infrared spectra, thermogravimetric analysis, X‐ray diffraction and UV‐visible spectra. The UV‐visible spectra showed that PThOD could absorb not only in the whole ultraviolet range from 200 to 400 nm but also in the visible light range up to 500 nm. Considering the conjugated structure of PThOD, studies were carried out of its performance for the photocatalytic degradation of various dyes, such as methyl orange, methylene blue, rhodamine B and reactive brilliant blue (RBB), under medium‐pressure Hg light source irradiation. The results showed that PThOD was an effective photocatalyst, which could degrade the four types of dye solution. Besides, visible light was also used to investigate the degradation of RBB, and the results showed that RBB could be degraded as well, though the efficiency was not as high as using the Hg lamp. The superoxide anion radical (O₂^??), which is one of the reactive oxide species, was detected using the nitrotetrazolium blue chloride method and considered to play a key role in photodegradation of dyes. Moreover, various scavengers were also used to further prove the function of ^?. Furthermore, it was found that degradation rate could be changed by adding H⁺, which might be attributed to a change of adsorption capacity of PThOD. Finally, the reusability of PThOD as photocatalyst was investigated. The results indicated that the reusability efficiency of PThOD was excellent even after ten continuous rounds of use. © 2018 Society of Chemical Industry