A Facile One-Pot Synthesis of Biomimetic Photocatalyst Zn(II)-Porphyrin-Sensitized 3D TiO2 Hollow Nanoboxes and Synergistically Enhanced Visible-Light Degradation

Abstract

A serials of biomimetic photocatalyst zinc(II) meso-tetra(4-carboxyphenyl)porphyrinato (ZnTCP)-sensitized 3D hierarchical TiO₂ hollow nanoboxes (TiO₂-HNBs) assembled by six ordered nanosheets with dominant {001} facets exposure (ZnTCP@TiO₂-HNBs) have been successfully synthesized by a facile one-pot solvothermal method via a topological transformation process with TiOF₂ as template. Infrared spectra (IR), UV-vis spectroscopy, and X-ray photoelectron spectroscopy (XPS) confirmed that ZnTCP played a decisive role in constructing 3D hollow nanoboxes through the formation of ester bond combined to TiO₂-HNBs, which also provided a transferring photo excited electrons bridge to sensitize TiO₂-HNBs for enhancing visible-light response. Due to the superior sensitization and biomimetic activity of ZnTCP, the photodegradation rate of rhodamine B (RhB) of as-prepared ZnTCP@TiO₂-HNBs with ZnTCP/TiOF₂ mass ratio of 2% (T-2p) improves 3.6 times compared to that of TiO₂-HNBs with a degradation yield of 99% for 2 h under simulated sunlight irradiation (> 420 nm). The enhanced photodegradation ability was attributed to synergistic visible photocatalytic mechanism of biomimetic catalyst, which can not only produce hydroxyl radical (•OH) and superoxide radical (•O₂⁻) coming from the excitation process of ZnTCP sensitized TiO₂-HNBs, but also generate singlet oxygen (¹O₂) that was only provided by biomimetic enzyme porphyrins. Furthermore, the photocatalyst showed good recycling stability and dispersibility after five rounds, ascribed to ZnTCP strong chemical bonding to the support TiO₂-HNBs. By means of electrochemical cyclic voltammetry analysis, the effect of central zinc ions and parent porphyrin rings on the redox property of biomimetic catalyst was studied.