UV-switchable phosphotungstic acid sandwiched between ZIF-8 and Au nanoparticles to improve simultaneous adsorption and UV light photocatalysis toward tetracycline degradation

In this work, a facile approach was introduced for the local synthesis of Au nanoparticle-decorated polyoxometalate/Zeolitic Imidazolate Framework-8 nanostructure (denoted ZIF-8@PTA@AuNP) to prepare highly active adsorbent and photocatalyst. For this aim, phosphotungstic acid (PTA) was used as a locally reducing agent and molecular bridge between Au nanoparticles and ZeoliticImidazolate Framework-8 (ZIF-8). The prepared nanostructure was characterised using different methods, including XRD, FTIR, EDX, TEM, BET, TGA and DRS. The band gap energy (E_g) value of the nanostructure was 1.13 eV, which is significantly lower than pristine ZIF-8. The prepared nanostructure was employed for the removal of tetracycline pharmaceutical compound from aqueous solution through simultaneous adsorption and photocatalytic processes and the results revealed that the presence of both PTA and Au nanoparticles on the surface of ZIF-8 can have a remarkable effect on the enhancement of adsorption and on the photocatalyticperformance of the system. However, it exhibited high behaviour in a wide range of pH, but the optimum condition was found at pH 7. A plausible photocatalytic mechanism was proposed. Also, the prepared nanostructure may have wide potential implications for the degradation of organic species.