A spherical deca-vanadophosphate covalent assembled all-inorganic open framework

Green synthesis of Ag/TiO2 composite coated porous vanadophosphates with enhanced visible-light photo-degradation and catalytic reduction performance for removing organic dyes

As environmental pollution and energy shortages have become global concerns, the construction of highly efficient catalysts using facile and green methods remains a long-term goal. In the present study, we proposed a facile catalyst preparation method in which Ag/TiO₂ composites were coated on the surface of the porous pure inorganic crystalline vanadium phosphates (VPO) by a one-step strategy. More importantly, the in situ reduction of Ag nanoparticles was achieved at room temperature without severe conditions or hydrogen atmosphere in which the porous VPO was employed as the reductant. The prepared Ag/VPO@TiO₂ composites act as a class of efficient bifunctional catalysts for visible light photodegradation of MB molecules and catalytic reduction of p-nitrophenol (4-NP). Among these samples, the 6.82%Ag/VPO@TiO₂ composite exhibited a superior photocatalytic activity in the degradation of MB and an ultrafast reduction rate for 4-NP of about 0.1 mM/40 s. The photocatalytic mechanistic studies revealed that the encapsulated VPO with a narrow band gap not only efficiently enhances the photosensitivity of the TiO₂ but also largely facilitates the photogenerated charge separation. The subsequent deposition of Ag NPs is able to further promote electron transfer ability, which leads to the higher photocatalytic activity. Moreover, the contact of Ag NPs with the surface of semiconductor TiO₂ can result in an electron-enhanced area in their interface that could effectively facilitate the uptake of electrons by the 4-NP molecules and then improve the reduction activity.