Polar peripheral substituent-regulated organic/inorganic hybrid photocatalysts promoting the degradation of phenolic pollutants

Constructing surface hybrid inorganic semiconductor photocatalysts with π conjugated structure is considered as an efficient way to improve the photocatalytic performance. Herein, by using porphyrin as light harvester and electron donor, BiOI as electron acceptor and active center, novel inorganic/organic (porphyrin/BiOI) hybrid photocatalysts with improved performance were prepared using impregnation method in non-covalent way. To explore the effects of porphyrin peripheral substituents on the performance of hybrid photocatalysts, four porphyrin/BiOI hybrids with different polar groups (–COOH, –OH, –NH2, –NO2) on the porphyrin substituents were prepared and their performances in the photocatalytic degradation of four phenolic pollutants were evaluated. All porphyrin/BiOI hybrids showed greatly improved photocatalytic activities compared to BiOI, and TCPP/BiOI hybrid containing –COOH groups was the best one. Under visible light irradiation, TCPP/BiOI could realise 100% photodegradation of 4-chlorophenol (4-CP) within 60 min, whose apparent kinetic constant was about 9.4 times that of BiOI. Substantial experimental results and theoretical calculation suggest that the different photocatalytic performances of the porphyrin/BiOI hybrids containing different porphyrin peripheral groups (–NO2 < –NH2 < –OH <–COOH) are highly correlated with the orientation of the dipole moment and the polarity of porphyrin substituent. This work illustrates that fine-tuning of the sensitizer molecular structure is essential to improve the photocatalytic activity of organic molecule-sensitized semiconductors.