Lacunary Keggin-type polyoxometalates-based macroporous composite films: preparation and photocatalytic activity Original Research Article

A simple method for the fabrication of highly ordered macroporous composite films, [Xn+W11O39](12−n)−–MO2 (abbreviated XW11–MO2, X: P, Si, and Ge; M: Si and Ti), is described. That is, mono-dispersed colloidal polystyrene (PS) particles were first assembled on quartz slides by utilizing capillary force. Then XW11–MO2 sol infiltrated into the voids between these template PS spheres on the slides by a spin-coating technique. After the composite films were dried at room temperature, PS spheres were removed by extraction in ultrasound. Highly ordered macroporous composite films formed; the surface morphology of these films was characterized by scanning electron microscopy (SEM). The surfaces of these films are highly uniform, and the size of the pores is in the range of 300–450 nm. The photocatalytic performances of different macroporous composite films were compared via the degradation of aqueous dyes Rhodamine B (RB), Erythrosine BS (E-BS), Methyl Orange (MO) and Congo Red (CR) under UV irradiation. The composite PW11–TiO2 film showed higher photoactivity than did the PW11–SiO2 film. This difference is attributed to a synergistic effect of the combination of polyoxometalates (POMs) and titanium dioxide.