PHOTOCATALYTIC ACTIVITIES of Ag+ DOPED ZIF-8 and ZIF-L CRYSTALS

Abstract

Photocatalysis is expected to contribute to the solution of environmental problems such as water and air pollution in the near future. The design of photocatalysts with high electron-hole generation rates, high surface areas and high light absorption capacities is crucial in producing sustainable and cost-effective photocatalytic processes. Titania, zirconia, copper oxide, zinc oxide, iron oxide are widely used photocatalysts which have good light absorption capacities with moderate surface areas depending on the synthesis conditions. In the last decade metal organic frameworks (MOFs) have been used in photocatalytic applications due to their very high surface areas up to 1000s of m²/g and adequate light absorption capacities. In this study zeolitic imidazolate framework (ZIF) based MOF photocatalytsts were prepared and the effect of silver (Ag) doping on the photocatalytic activity of ZIF-8 and ZIF-L crystals was investigated. Ag doped ZIF-8 and ZIF-L crystals were prepared and their activities in the photocatalytic removal of methylene blue (MB) dye under UV irradiation were determined for the first time in the literature. Doped ZIF-8 and ZIF-L crystals showed better photocatalytic activities compared to the undoped crystals. 100% of MB was removed with 5 mole% Ag⁺ doped ZIF-8 in 40 min. The photocatalytic activity decreased beyond 5% doping level since Ag⁺ ions may have segregated due to a possible solid state solubility limit of Ag⁺ ions in the crystal lattice of ZIF-8. ZIF-L crystals possessed lower photocatalytic activities compared to ZIF-8 crystals.

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