Enhancement of the photocatalytic performance and thermal stability of an iron based metal–organic-framework functionalised by Ag/Ag3PO4

Abstract

Metal–organic-frameworks have been reported as potential photocatalyst candidates due to their high surface area and semiconductive behaviour, but due to their high charge recombination rate and low visible light harvesting efficiency their use as photocatalysts has remained a challenge. A promising strategy to overcome these shortcomings is the construction of hybrid nanocomposite photocatalysts which reduce the recombination of charge carriers and simultaneously enhance the light harvesting efficiency. Herein, we report the microwave-assisted design of a novel visible light active composite material consisting of an iron-based metal–organic-framework functionalised by Ag/Ag₃PO₄. The resulting composite material demonstrates that both Ag₃PO₄ and MIL-53(Fe) show improved charge separation involving a Z-scheme internal charge transmission mechanism via ‘Ag’ nanoparticles (Ag⁰ NPs). The high dispersion of Ag⁰ and Ag₃PO₄ NPs and their close contact with the MIL-53(Fe) matrix help to degrade the organic pollutants effectively under visible light due to their synergistic effects. The photocatalytic degradation of a hazardous sulfonated azo dye Ponceau BS was carried out under visible light irradiation and Ag/Ag₃PO₄/MIL-53(Fe) was found to exhibit the highest photocatalytic performance. In addition, thermogravimetric analysis reveals that functionalization of MIL-53(Fe) by Ag/Ag₃PO₄/increases the thermal stability of MIL-53(Fe) which is attributed to the strengthening of an organic linker attached to iron due to the interaction of Ag/Ag₃PO₄ with the framework. Scavenger experiments supported the proposed Z-scheme internal charge separation. Moreover, the reusability experiments clearly indicate the high stability of the catalysts.