Size effect of gold nanoparticles in bimetallic ZIF catalysts for enhanced photo-redox reactions

It is well known that gold nanoparticles have been widely used in various photo-redox reactions because of the unique surface plasmon resonance effect and the excellent internal electron transfer ability. However, the essential factors of how the metal nanoparticles enhancing the activity of photocatalysts have not been fully revealed. In this paper, gold colloidal particles of different sizes were modified on the surface of the dodecahedral skeleton of ZIF-Co/Zn. The photocatalytic activity of Au@ZIF-Co/Zn was investigated under simulated visible light for treating Rhodamine B/Cr(VI) mixture solutions (RhB/Cr(VI) 20 mg/L) and 4-nitrophenol solution (4-NP 20 mg/L). The results indicate that the size of gold nanoparticles could affect the surface plasmon resonance effect observably, internal electron transfer capacity and carrier density change. Photoelectric chemistry experiments and radical quenching experiments were performed to reveal the charge-transfer photocatalytic mechanism and size influence of gold nanoparticles in composite photocatalysts. This work may provide a novel strategy for the construction of metal–organic frameworks for the purification of wastewater mixed with heavy metal ions, organic pollutants and pharmaceutical intermediates.