Conjugated microporous polymer bearing 1,3,4-oxadiazole and thienyl moieties for decomposition of organic dyes under visible light

Conjugated microporous polymers (CMPs), as heterogeneous catalysts, have been studied intensively in the past few years. Here we reported two rationally designed and synthesized novel CMPs as the photocatalysts for degradation of organic dyes. The CMPs were synthesized by typical Suzuki polycondensation method and confirmed by FTIR and 13C solid-state NMR. The band gap energies of both CMPs were 3.1 eV for Ph(PhXOD)3-CMP and 2.5 eV for Ph(ThXOD)3-CMP, respectively, calculated by UV–vis spectra, indicating that the latter could be activated by visible light. The BET results showed that the Ph(PhXOD)3-CMP (349.3 m2/g) had much higher surface areas than that of Ph(ThXOD)3-CMP (78.2 m2/g). The photodegradation of organic dyes experiments showed that the Ph(PhXOD)3-CMP only presented photocatalytic ability on the condition of ultraviolet irradiation due to lack of absorption in visible light region. While Ph(ThXOD)3-CMP exhibited a relatively strong photocatalytic ability to initiate degradation of RhB and MB dye solution with visible light irradiation. Specifically, the RhB solution (10 mg/L) could be decolorized in 150 min when Ph(ThXOD)3-CMP was used as the photocatalyst under visible light. The mechanism study including adding-scavenger method, NBT method and ESR characterization showed that the superoxide anion radical was the dominant active species during photodegradation of RhB. This research was expected to inspire more research interest in the rational design of CMPs for photodegradation of organic dyes.