Coordinative integration of a metal-porphyrinic framework and TiO2 nanoparticles for the formation of composite photocatalysts with enhanced visible-light-driven photocatalytic activities

Abstract

The development of efficient catalysts with a visible-light response is of great importance in photocatalysis. Porphyrinic metal-organic frameworks (porph-MOFs) have recently been shown as promising photocatalyst candidates due to their large surface area, high visible light harvesting efficiency, and semiconductive properties, but challenges still remain because of their rapid charge recombination. Herein, we report the design of an effectively visible-light-driven composite material, namely TP-222(Zn), containing zirconium-based porph-MOF PCN-222(Zn) linked TiO₂ nanoparticles (NPs) via the compound 4-mercaptopyridine which is axially bonded to the porphyrin central Zn metal in the PCN-222(Zn) and anchored onto the surface of TiO₂ NPs. The resulting composite material demonstrates the high dispersion of TiO₂ NPs and their close contact with the porph-MOF matrix, and serves as an effective photocatalyst for degrading organic contaminants under visible light irradiation due to their synergistic effect. It is further confirmed by fluorescence spectroscopy and electrochemical impedance spectroscopy that the remarkably enhanced photocatalytic activity of the TP-222(Zn) composite is attributed to the efficient charge separation with electron injection from PCN-222(Zn) to TiO₂ NPs. In addition, the TP-222(Zn) composite shows excellent stability and recyclability as a result of the axially coordinative interaction between TiO₂ NPs/PCN-222(Zn) and the 4-mercaptopyridine. Overall, this work provides a new strategy for the fabrication of highly efficient porph-MOF-based composite materials for visible light-driven photocatalysis.